Add int_size option for generator.
[apps/agl-service-can-low-level.git] / pb_decode.c
index 379d134..b5ec1ef 100644 (file)
  * 2011 Petteri Aimonen <jpa@kapsi.fi>
  */
 
+/* Use the GCC warn_unused_result attribute to check that all return values
+ * are propagated correctly. On other compilers and gcc before 3.4.0 just
+ * ignore the annotation.
+ */
+#if !defined(__GNUC__) || ( __GNUC__ < 3) || (__GNUC__ == 3 && __GNUC_MINOR__ < 4)
+    #define checkreturn
+#else
+    #define checkreturn __attribute__((warn_unused_result))
+#endif
+
 #include "pb.h"
 #include "pb_decode.h"
-#include <string.h>
+#include "pb_common.h"
 
-typedef bool (*pb_decoder_t)(pb_istream_t *stream, const pb_field_t *field, void *dest);
+/**************************************
+ * Declarations internal to this file *
+ **************************************/
+
+typedef bool (*pb_decoder_t)(pb_istream_t *stream, const pb_field_t *field, void *dest) checkreturn;
+
+static bool checkreturn buf_read(pb_istream_t *stream, uint8_t *buf, size_t count);
+static bool checkreturn pb_decode_varint32(pb_istream_t *stream, uint32_t *dest);
+static bool checkreturn read_raw_value(pb_istream_t *stream, pb_wire_type_t wire_type, uint8_t *buf, size_t *size);
+static bool checkreturn decode_static_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iter_t *iter);
+static bool checkreturn decode_callback_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iter_t *iter);
+static bool checkreturn decode_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iter_t *iter);
+static void iter_from_extension(pb_field_iter_t *iter, pb_extension_t *extension);
+static bool checkreturn default_extension_decoder(pb_istream_t *stream, pb_extension_t *extension, uint32_t tag, pb_wire_type_t wire_type);
+static bool checkreturn decode_extension(pb_istream_t *stream, uint32_t tag, pb_wire_type_t wire_type, pb_field_iter_t *iter);
+static bool checkreturn find_extension_field(pb_field_iter_t *iter);
+static void pb_field_set_to_default(pb_field_iter_t *iter);
+static void pb_message_set_to_defaults(const pb_field_t fields[], void *dest_struct);
+static bool checkreturn pb_dec_varint(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_dec_uvarint(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_dec_svarint(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_dec_fixed32(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_dec_fixed64(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_dec_bytes(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_dec_string(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_dec_submessage(pb_istream_t *stream, const pb_field_t *field, void *dest);
+static bool checkreturn pb_skip_varint(pb_istream_t *stream);
+static bool checkreturn pb_skip_string(pb_istream_t *stream);
+
+#ifdef PB_ENABLE_MALLOC
+static bool checkreturn allocate_field(pb_istream_t *stream, void *pData, size_t data_size, size_t array_size);
+static void pb_release_single_field(const pb_field_iter_t *iter);
+#endif
 
 /* --- Function pointers to field decoders ---
  * Order in the array must match pb_action_t LTYPE numbering.
  */
 static const pb_decoder_t PB_DECODERS[PB_LTYPES_COUNT] = {
     &pb_dec_varint,
+    &pb_dec_uvarint,
     &pb_dec_svarint,
-    &pb_dec_fixed,
+    &pb_dec_fixed32,
+    &pb_dec_fixed64,
     
     &pb_dec_bytes,
     &pb_dec_string,
-    &pb_dec_submessage
+    &pb_dec_submessage,
+    NULL /* extensions */
 };
 
-/**************
- * pb_istream *
- **************/
+/*******************************
+ * pb_istream_t implementation *
+ *******************************/
 
-bool pb_read(pb_istream_t *stream, uint8_t *buf, size_t count)
+static bool checkreturn buf_read(pb_istream_t *stream, uint8_t *buf, size_t count)
 {
+    uint8_t *source = (uint8_t*)stream->state;
+    stream->state = source + count;
+    
+    if (buf != NULL)
+    {
+        while (count--)
+            *buf++ = *source++;
+    }
+    
+    return true;
+}
+
+bool checkreturn pb_read(pb_istream_t *stream, uint8_t *buf, size_t count)
+{
+#ifndef PB_BUFFER_ONLY
+       if (buf == NULL && stream->callback != buf_read)
+       {
+               /* Skip input bytes */
+               uint8_t tmp[16];
+               while (count > 16)
+               {
+                       if (!pb_read(stream, tmp, 16))
+                               return false;
+                       
+                       count -= 16;
+               }
+               
+               return pb_read(stream, tmp, count);
+       }
+#endif
+
     if (stream->bytes_left < count)
-        return false;
+        PB_RETURN_ERROR(stream, "end-of-stream");
     
+#ifndef PB_BUFFER_ONLY
     if (!stream->callback(stream, buf, count))
+        PB_RETURN_ERROR(stream, "io error");
+#else
+    if (!buf_read(stream, buf, count))
         return false;
+#endif
     
     stream->bytes_left -= count;
     return true;
 }
 
-static bool buf_read(pb_istream_t *stream, uint8_t *buf, size_t count)
+/* Read a single byte from input stream. buf may not be NULL.
+ * This is an optimization for the varint decoding. */
+static bool checkreturn pb_readbyte(pb_istream_t *stream, uint8_t *buf)
 {
-    uint8_t *source = (uint8_t*)stream->state;
-    
-    if (buf != NULL)
-        memcpy(buf, source, count);
+    if (stream->bytes_left == 0)
+        PB_RETURN_ERROR(stream, "end-of-stream");
+
+#ifndef PB_BUFFER_ONLY
+    if (!stream->callback(stream, buf, 1))
+        PB_RETURN_ERROR(stream, "io error");
+#else
+    *buf = *(uint8_t*)stream->state;
+    stream->state = (uint8_t*)stream->state + 1;
+#endif
+
+    stream->bytes_left--;
     
-    stream->state = source + count;
-    return true;
+    return true;    
 }
 
 pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize)
 {
     pb_istream_t stream;
+#ifdef PB_BUFFER_ONLY
+    stream.callback = NULL;
+#else
     stream.callback = &buf_read;
+#endif
     stream.state = buf;
     stream.bytes_left = bufsize;
+#ifndef PB_NO_ERRMSG
+    stream.errmsg = NULL;
+#endif
     return stream;
 }
 
@@ -62,33 +159,65 @@ pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize)
  * Helper functions *
  ********************/
 
-static bool pb_decode_varint32(pb_istream_t *stream, uint32_t *dest)
+static bool checkreturn pb_decode_varint32(pb_istream_t *stream, uint32_t *dest)
 {
-    uint64_t temp;
-    bool status = pb_decode_varint(stream, &temp);
-    *dest = temp;
-    return status;
+    uint8_t byte;
+    uint32_t result;
+    
+    if (!pb_readbyte(stream, &byte))
+        return false;
+    
+    if ((byte & 0x80) == 0)
+    {
+        /* Quick case, 1 byte value */
+        result = byte;
+    }
+    else
+    {
+        /* Multibyte case */
+        uint8_t bitpos = 7;
+        result = byte & 0x7F;
+        
+        do
+        {
+            if (bitpos >= 32)
+                PB_RETURN_ERROR(stream, "varint overflow");
+            
+            if (!pb_readbyte(stream, &byte))
+                return false;
+            
+            result |= (uint32_t)(byte & 0x7F) << bitpos;
+            bitpos = (uint8_t)(bitpos + 7);
+        } while (byte & 0x80);
+   }
+   
+   *dest = result;
+   return true;
 }
 
-bool pb_decode_varint(pb_istream_t *stream, uint64_t *dest)
+bool checkreturn pb_decode_varint(pb_istream_t *stream, uint64_t *dest)
 {
     uint8_t byte;
-    int bitpos = 0;
-    *dest = 0;
+    uint8_t bitpos = 0;
+    uint64_t result = 0;
     
-    while (bitpos < 64 && pb_read(stream, &byte, 1))
+    do
     {
-        *dest |= (uint64_t)(byte & 0x7F) << bitpos;
-        bitpos += 7;
+        if (bitpos >= 64)
+            PB_RETURN_ERROR(stream, "varint overflow");
         
-        if (!(byte & 0x80))
-            return true;
-    }
+        if (!pb_readbyte(stream, &byte))
+            return false;
+
+        result |= (uint64_t)(byte & 0x7F) << bitpos;
+        bitpos = (uint8_t)(bitpos + 7);
+    } while (byte & 0x80);
     
-    return false;
+    *dest = result;
+    return true;
 }
 
-bool pb_skip_varint(pb_istream_t *stream)
+bool checkreturn pb_skip_varint(pb_istream_t *stream)
 {
     uint8_t byte;
     do
@@ -99,7 +228,7 @@ bool pb_skip_varint(pb_istream_t *stream)
     return true;
 }
 
-bool pb_skip_string(pb_istream_t *stream)
+bool checkreturn pb_skip_string(pb_istream_t *stream)
 {
     uint32_t length;
     if (!pb_decode_varint32(stream, &length))
@@ -108,12 +237,33 @@ bool pb_skip_string(pb_istream_t *stream)
     return pb_read(stream, NULL, length);
 }
 
-/* Currently the wire type related stuff is kept hidden from
- * callbacks. They shouldn't need it. It's better for performance
- * to just assume the correct type and fail safely on corrupt message.
- */
+bool checkreturn pb_decode_tag(pb_istream_t *stream, pb_wire_type_t *wire_type, uint32_t *tag, bool *eof)
+{
+    uint32_t temp;
+    *eof = false;
+    *wire_type = (pb_wire_type_t) 0;
+    *tag = 0;
+    
+    if (!pb_decode_varint32(stream, &temp))
+    {
+        if (stream->bytes_left == 0)
+            *eof = true;
 
-static bool skip(pb_istream_t *stream, int wire_type)
+        return false;
+    }
+    
+    if (temp == 0)
+    {
+        *eof = true; /* Special feature: allow 0-terminated messages. */
+        return false;
+    }
+    
+    *tag = temp >> 3;
+    *wire_type = (pb_wire_type_t)(temp & 7);
+    return true;
+}
+
+bool checkreturn pb_skip_field(pb_istream_t *stream, pb_wire_type_t wire_type)
 {
     switch (wire_type)
     {
@@ -121,14 +271,14 @@ static bool skip(pb_istream_t *stream, int wire_type)
         case PB_WT_64BIT: return pb_read(stream, NULL, 8);
         case PB_WT_STRING: return pb_skip_string(stream);
         case PB_WT_32BIT: return pb_read(stream, NULL, 4);
-        default: return false;
+        default: PB_RETURN_ERROR(stream, "invalid wire_type");
     }
 }
 
 /* Read a raw value to buffer, for the purpose of passing it to callback as
  * a substream. Size is maximum size on call, and actual size on return.
  */
-static bool read_raw_value(pb_istream_t *stream, pb_wire_type_t wire_type, uint8_t *buf, size_t *size)
+static bool checkreturn read_raw_value(pb_istream_t *stream, pb_wire_type_t wire_type, uint8_t *buf, size_t *size)
 {
     size_t max_size = *size;
     switch (wire_type)
@@ -151,12 +301,14 @@ static bool read_raw_value(pb_istream_t *stream, pb_wire_type_t wire_type, uint8
             *size = 4;
             return pb_read(stream, buf, 4);
         
-        default: return false;
+        default: PB_RETURN_ERROR(stream, "invalid wire_type");
     }
 }
 
-/* Decode string length from stream and return a substream with limited length */
-static bool make_string_substream(pb_istream_t *stream, pb_istream_t *substream)
+/* Decode string length from stream and return a substream with limited length.
+ * Remember to close the substream using pb_close_string_substream().
+ */
+bool checkreturn pb_make_string_substream(pb_istream_t *stream, pb_istream_t *substream)
 {
     uint32_t size;
     if (!pb_decode_varint32(stream, &size))
@@ -164,315 +316,916 @@ static bool make_string_substream(pb_istream_t *stream, pb_istream_t *substream)
     
     *substream = *stream;
     if (substream->bytes_left < size)
-        return false;
+        PB_RETURN_ERROR(stream, "parent stream too short");
     
     substream->bytes_left = size;
     stream->bytes_left -= size;
     return true;
 }
 
-/* Iterator for pb_field_t list */
-typedef struct {
-    const pb_field_t *start;
-    const pb_field_t *current;
-    int field_index;
-    void *dest_struct;
-    void *pData;
-    void *pSize;
-} pb_field_iterator_t;
-
-static void pb_field_init(pb_field_iterator_t *iter, const pb_field_t *fields, void *dest_struct)
+void pb_close_string_substream(pb_istream_t *stream, pb_istream_t *substream)
 {
-    iter->start = iter->current = fields;
-    iter->field_index = 0;
-    iter->pData = dest_struct;
-    iter->dest_struct = dest_struct;
-}
-
-static bool pb_field_next(pb_field_iterator_t *iter)
-{
-    bool notwrapped = true;
-    size_t prev_size = iter->current->data_size * iter->current->array_size;
-    iter->current++;
-    iter->field_index++;
-    if (iter->current->tag == 0)
-    {
-        iter->current = iter->start;
-        iter->field_index = 0;
-        iter->pData = iter->dest_struct;
-        prev_size = 0;
-        notwrapped = false;
-    }
-    
-    iter->pData = (char*)iter->pData + prev_size + iter->current->data_offset;
-    iter->pSize = (char*)iter->pData + iter->current->size_offset;
-    return notwrapped;
-}
+    stream->state = substream->state;
 
-static bool pb_field_find(pb_field_iterator_t *iter, int tag)
-{
-    int start = iter->field_index;
-    
-    do {
-        if (iter->current->tag == tag)
-            return true;
-        pb_field_next(iter);
-    } while (iter->field_index != start);
-    
-    return false;
+#ifndef PB_NO_ERRMSG
+    stream->errmsg = substream->errmsg;
+#endif
 }
 
 /*************************
  * Decode a single field *
  *************************/
 
-static bool decode_field(pb_istream_t *stream, int wire_type, pb_field_iterator_t *iter)
+static bool checkreturn decode_static_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iter_t *iter)
 {
-    pb_decoder_t func = PB_DECODERS[PB_LTYPE(iter->current->type)];
+    pb_type_t type;
+    pb_decoder_t func;
     
-    switch (PB_HTYPE(iter->current->type))
+    type = iter->pos->type;
+    func = PB_DECODERS[PB_LTYPE(type)];
+
+    switch (PB_HTYPE(type))
     {
         case PB_HTYPE_REQUIRED:
-            return func(stream, iter->current, iter->pData);
+            return func(stream, iter->pos, iter->pData);
             
         case PB_HTYPE_OPTIONAL:
             *(bool*)iter->pSize = true;
-            return func(stream, iter->current, iter->pData);
+            return func(stream, iter->pos, iter->pData);
     
-        case PB_HTYPE_ARRAY:
+        case PB_HTYPE_REPEATED:
             if (wire_type == PB_WT_STRING
-                && PB_LTYPE(iter->current->type) <= PB_LTYPE_LAST_PACKABLE)
+                && PB_LTYPE(type) <= PB_LTYPE_LAST_PACKABLE)
             {
                 /* Packed array */
-                size_t *size = (size_t*)iter->pSize;
+                bool status = true;
+                pb_size_t *size = (pb_size_t*)iter->pSize;
                 pb_istream_t substream;
-                if (!make_string_substream(stream, &substream))
+                if (!pb_make_string_substream(stream, &substream))
                     return false;
                 
-                while (substream.bytes_left && *size < iter->current->array_size)
+                while (substream.bytes_left > 0 && *size < iter->pos->array_size)
                 {
-                    void *pItem = (uint8_t*)iter->pData + iter->current->data_size * (*size);
-                    if (!func(stream, iter->current, pItem))
-                        return false;
+                    void *pItem = (uint8_t*)iter->pData + iter->pos->data_size * (*size);
+                    if (!func(&substream, iter->pos, pItem))
+                    {
+                        status = false;
+                        break;
+                    }
                     (*size)++;
                 }
-                return (substream.bytes_left == 0);
+                pb_close_string_substream(stream, &substream);
+                
+                if (substream.bytes_left != 0)
+                    PB_RETURN_ERROR(stream, "array overflow");
+                
+                return status;
             }
             else
             {
                 /* Repeated field */
-                size_t *size = (size_t*)iter->pSize;
-                void *pItem = (uint8_t*)iter->pData + iter->current->data_size * (*size);
-                if (*size >= iter->current->array_size)
-                    return false;
+                pb_size_t *size = (pb_size_t*)iter->pSize;
+                void *pItem = (uint8_t*)iter->pData + iter->pos->data_size * (*size);
+                if (*size >= iter->pos->array_size)
+                    PB_RETURN_ERROR(stream, "array overflow");
                 
                 (*size)++;
-                return func(stream, iter->current, pItem);
+                return func(stream, iter->pos, pItem);
+            }
+
+        default:
+            PB_RETURN_ERROR(stream, "invalid field type");
+    }
+}
+
+#ifdef PB_ENABLE_MALLOC
+/* Allocate storage for the field and store the pointer at iter->pData.
+ * array_size is the number of entries to reserve in an array.
+ * Zero size is not allowed, use pb_free() for releasing.
+ */
+static bool checkreturn allocate_field(pb_istream_t *stream, void *pData, size_t data_size, size_t array_size)
+{    
+    void *ptr = *(void**)pData;
+    
+    if (data_size == 0 || array_size == 0)
+        PB_RETURN_ERROR(stream, "invalid size");
+    
+    /* Check for multiplication overflows.
+     * This code avoids the costly division if the sizes are small enough.
+     * Multiplication is safe as long as only half of bits are set
+     * in either multiplicand.
+     */
+    {
+        const size_t check_limit = (size_t)1 << (sizeof(size_t) * 4);
+        if (data_size >= check_limit || array_size >= check_limit)
+        {
+            const size_t size_max = (size_t)-1;
+            if (size_max / array_size < data_size)
+            {
+                PB_RETURN_ERROR(stream, "size too large");
+            }
+        }
+    }
+    
+    /* Allocate new or expand previous allocation */
+    /* Note: on failure the old pointer will remain in the structure,
+     * the message must be freed by caller also on error return. */
+    ptr = pb_realloc(ptr, array_size * data_size);
+    if (ptr == NULL)
+        PB_RETURN_ERROR(stream, "realloc failed");
+    
+    *(void**)pData = ptr;
+    return true;
+}
+
+/* Clear a newly allocated item in case it contains a pointer, or is a submessage. */
+static void initialize_pointer_field(void *pItem, pb_field_iter_t *iter)
+{
+    if (PB_LTYPE(iter->pos->type) == PB_LTYPE_STRING ||
+        PB_LTYPE(iter->pos->type) == PB_LTYPE_BYTES)
+    {
+        *(void**)pItem = NULL;
+    }
+    else if (PB_LTYPE(iter->pos->type) == PB_LTYPE_SUBMESSAGE)
+    {
+        pb_message_set_to_defaults((const pb_field_t *) iter->pos->ptr, pItem);
+    }
+}
+#endif
+
+static bool checkreturn decode_pointer_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iter_t *iter)
+{
+#ifndef PB_ENABLE_MALLOC
+    PB_UNUSED(wire_type);
+    PB_UNUSED(iter);
+    PB_RETURN_ERROR(stream, "no malloc support");
+#else
+    pb_type_t type;
+    pb_decoder_t func;
+    
+    type = iter->pos->type;
+    func = PB_DECODERS[PB_LTYPE(type)];
+    
+    switch (PB_HTYPE(type))
+    {
+        case PB_HTYPE_REQUIRED:
+        case PB_HTYPE_OPTIONAL:
+            if (PB_LTYPE(type) == PB_LTYPE_SUBMESSAGE &&
+                *(void**)iter->pData != NULL)
+            {
+                /* Duplicate field, have to release the old allocation first. */
+                pb_release_single_field(iter);
             }
         
-        case PB_HTYPE_CALLBACK:
-            if (wire_type == PB_WT_STRING)
+            if (PB_LTYPE(type) == PB_LTYPE_STRING ||
+                PB_LTYPE(type) == PB_LTYPE_BYTES)
+            {
+                return func(stream, iter->pos, iter->pData);
+            }
+            else
+            {
+                if (!allocate_field(stream, iter->pData, iter->pos->data_size, 1))
+                    return false;
+                
+                initialize_pointer_field(*(void**)iter->pData, iter);
+                return func(stream, iter->pos, *(void**)iter->pData);
+            }
+    
+        case PB_HTYPE_REPEATED:
+            if (wire_type == PB_WT_STRING
+                && PB_LTYPE(type) <= PB_LTYPE_LAST_PACKABLE)
             {
-                pb_callback_t *pCallback = (pb_callback_t*)iter->pData;
+                /* Packed array, multiple items come in at once. */
+                bool status = true;
+                pb_size_t *size = (pb_size_t*)iter->pSize;
+                size_t allocated_size = *size;
+                void *pItem;
                 pb_istream_t substream;
                 
-                if (!make_string_substream(stream, &substream))
+                if (!pb_make_string_substream(stream, &substream))
                     return false;
                 
                 while (substream.bytes_left)
                 {
-                    if (!pCallback->funcs.decode(&substream, iter->current, pCallback->arg))
-                        return false;
+                    if ((size_t)*size + 1 > allocated_size)
+                    {
+                        /* Allocate more storage. This tries to guess the
+                         * number of remaining entries. Round the division
+                         * upwards. */
+                        allocated_size += (substream.bytes_left - 1) / iter->pos->data_size + 1;
+                        
+                        if (!allocate_field(&substream, iter->pData, iter->pos->data_size, allocated_size))
+                        {
+                            status = false;
+                            break;
+                        }
+                    }
+
+                    /* Decode the array entry */
+                    pItem = *(uint8_t**)iter->pData + iter->pos->data_size * (*size);
+                    initialize_pointer_field(pItem, iter);
+                    if (!func(&substream, iter->pos, pItem))
+                    {
+                        status = false;
+                        break;
+                    }
+                    
+                    if (*size == PB_SIZE_MAX)
+                    {
+#ifndef PB_NO_ERRMSG
+                        stream->errmsg = "too many array entries";
+#endif
+                        status = false;
+                        break;
+                    }
+                    
+                    (*size)++;
                 }
-                return true;
+                pb_close_string_substream(stream, &substream);
+                
+                return status;
             }
             else
             {
-                /* Copy the single scalar value to stack.
-                 * This is required so that we can limit the stream length,
-                 * which in turn allows to use same callback for packed and
-                 * not-packed fields. */
-                pb_istream_t substream;
-                pb_callback_t *pCallback = (pb_callback_t*)iter->pData;
-                uint8_t buffer[10];
-                size_t size = sizeof(buffer);
+                /* Normal repeated field, i.e. only one item at a time. */
+                pb_size_t *size = (pb_size_t*)iter->pSize;
+                void *pItem;
                 
-                if (!read_raw_value(stream, wire_type, buffer, &size))
-                    return false;
-                substream = pb_istream_from_buffer(buffer, size);
+                if (*size == PB_SIZE_MAX)
+                    PB_RETURN_ERROR(stream, "too many array entries");
                 
-                return pCallback->funcs.decode(&substream, iter->current, pCallback->arg);
+                (*size)++;
+                if (!allocate_field(stream, iter->pData, iter->pos->data_size, *size))
+                    return false;
+            
+                pItem = *(uint8_t**)iter->pData + iter->pos->data_size * (*size - 1);
+                initialize_pointer_field(pItem, iter);
+                return func(stream, iter->pos, pItem);
             }
             
         default:
+            PB_RETURN_ERROR(stream, "invalid field type");
+    }
+#endif
+}
+
+static bool checkreturn decode_callback_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iter_t *iter)
+{
+    pb_callback_t *pCallback = (pb_callback_t*)iter->pData;
+    
+#ifdef PB_OLD_CALLBACK_STYLE
+    void *arg = pCallback->arg;
+#else
+    void **arg = &(pCallback->arg);
+#endif
+    
+    if (pCallback->funcs.decode == NULL)
+        return pb_skip_field(stream, wire_type);
+    
+    if (wire_type == PB_WT_STRING)
+    {
+        pb_istream_t substream;
+        
+        if (!pb_make_string_substream(stream, &substream))
             return false;
+        
+        do
+        {
+            if (!pCallback->funcs.decode(&substream, iter->pos, arg))
+                PB_RETURN_ERROR(stream, "callback failed");
+        } while (substream.bytes_left);
+        
+        pb_close_string_substream(stream, &substream);
+        return true;
+    }
+    else
+    {
+        /* Copy the single scalar value to stack.
+         * This is required so that we can limit the stream length,
+         * which in turn allows to use same callback for packed and
+         * not-packed fields. */
+        pb_istream_t substream;
+        uint8_t buffer[10];
+        size_t size = sizeof(buffer);
+        
+        if (!read_raw_value(stream, wire_type, buffer, &size))
+            return false;
+        substream = pb_istream_from_buffer(buffer, size);
+        
+        return pCallback->funcs.decode(&substream, iter->pos, arg);
     }
 }
 
-/*********************
- * Decode all fields *
- *********************/
+static bool checkreturn decode_field(pb_istream_t *stream, pb_wire_type_t wire_type, pb_field_iter_t *iter)
+{
+    switch (PB_ATYPE(iter->pos->type))
+    {
+        case PB_ATYPE_STATIC:
+            return decode_static_field(stream, wire_type, iter);
+        
+        case PB_ATYPE_POINTER:
+            return decode_pointer_field(stream, wire_type, iter);
+        
+        case PB_ATYPE_CALLBACK:
+            return decode_callback_field(stream, wire_type, iter);
+        
+        default:
+            PB_RETURN_ERROR(stream, "invalid field type");
+    }
+}
 
-bool pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
+static void iter_from_extension(pb_field_iter_t *iter, pb_extension_t *extension)
 {
-    uint32_t fields_seen = 0; /* Used to check for required fields */
-    pb_field_iterator_t iter;
-    int i;
+    /* Fake a field iterator for the extension field.
+     * It is not actually safe to advance this iterator, but decode_field
+     * will not even try to. */
+    const pb_field_t *field = (const pb_field_t*)extension->type->arg;
+    (void)pb_field_iter_begin(iter, field, extension->dest);
+    iter->pData = extension->dest;
+    iter->pSize = &extension->found;
     
-    if (fields[0].tag == 0)
+    if (PB_ATYPE(field->type) == PB_ATYPE_POINTER)
     {
-        /* No fields -> nothing to do */
-        return pb_read(stream, NULL, stream->bytes_left);
+        /* For pointer extensions, the pointer is stored directly
+         * in the extension structure. This avoids having an extra
+         * indirection. */
+        iter->pData = &extension->dest;
     }
+}
+
+/* Default handler for extension fields. Expects a pb_field_t structure
+ * in extension->type->arg. */
+static bool checkreturn default_extension_decoder(pb_istream_t *stream,
+    pb_extension_t *extension, uint32_t tag, pb_wire_type_t wire_type)
+{
+    const pb_field_t *field = (const pb_field_t*)extension->type->arg;
+    pb_field_iter_t iter;
     
-    pb_field_init(&iter, fields, dest_struct);
+    if (field->tag != tag)
+        return true;
     
-    /* Initialize size/has fields and apply default values */
-    do
+    iter_from_extension(&iter, extension);
+    extension->found = true;
+    return decode_field(stream, wire_type, &iter);
+}
+
+/* Try to decode an unknown field as an extension field. Tries each extension
+ * decoder in turn, until one of them handles the field or loop ends. */
+static bool checkreturn decode_extension(pb_istream_t *stream,
+    uint32_t tag, pb_wire_type_t wire_type, pb_field_iter_t *iter)
+{
+    pb_extension_t *extension = *(pb_extension_t* const *)iter->pData;
+    size_t pos = stream->bytes_left;
+    
+    while (extension != NULL && pos == stream->bytes_left)
     {
-        if (PB_HTYPE(iter.current->type) == PB_HTYPE_OPTIONAL)
+        bool status;
+        if (extension->type->decode)
+            status = extension->type->decode(stream, extension, tag, wire_type);
+        else
+            status = default_extension_decoder(stream, extension, tag, wire_type);
+
+        if (!status)
+            return false;
+        
+        extension = extension->next;
+    }
+    
+    return true;
+}
+
+/* Step through the iterator until an extension field is found or until all
+ * entries have been checked. There can be only one extension field per
+ * message. Returns false if no extension field is found. */
+static bool checkreturn find_extension_field(pb_field_iter_t *iter)
+{
+    const pb_field_t *start = iter->pos;
+    
+    do {
+        if (PB_LTYPE(iter->pos->type) == PB_LTYPE_EXTENSION)
+            return true;
+        (void)pb_field_iter_next(iter);
+    } while (iter->pos != start);
+    
+    return false;
+}
+
+/* Initialize message fields to default values, recursively */
+static void pb_field_set_to_default(pb_field_iter_t *iter)
+{
+    pb_type_t type;
+    type = iter->pos->type;
+    
+    if (PB_LTYPE(type) == PB_LTYPE_EXTENSION)
+    {
+        pb_extension_t *ext = *(pb_extension_t* const *)iter->pData;
+        while (ext != NULL)
         {
-            *(bool*)iter.pSize = false;
-            
-            /* Initialize to default value */
-            if (iter.current->ptr != NULL)
-                memcpy(iter.pData, iter.current->ptr, iter.current->data_size);
+            pb_field_iter_t ext_iter;
+            ext->found = false;
+            iter_from_extension(&ext_iter, ext);
+            pb_field_set_to_default(&ext_iter);
+            ext = ext->next;
+        }
+    }
+    else if (PB_ATYPE(type) == PB_ATYPE_STATIC)
+    {
+        bool init_data = true;
+        if (PB_HTYPE(type) == PB_HTYPE_OPTIONAL)
+        {
+            /* Set has_field to false. Still initialize the optional field
+             * itself also. */
+            *(bool*)iter->pSize = false;
+        }
+        else if (PB_HTYPE(type) == PB_HTYPE_REPEATED)
+        {
+            /* Set array count to 0, no need to initialize contents. */
+            *(pb_size_t*)iter->pSize = 0;
+            init_data = false;
+        }
+        
+        if (init_data)
+        {
+            if (PB_LTYPE(iter->pos->type) == PB_LTYPE_SUBMESSAGE)
+            {
+                /* Initialize submessage to defaults */
+                pb_message_set_to_defaults((const pb_field_t *) iter->pos->ptr, iter->pData);
+            }
+            else if (iter->pos->ptr != NULL)
+            {
+                /* Initialize to default value */
+                memcpy(iter->pData, iter->pos->ptr, iter->pos->data_size);
+            }
             else
-                memset(iter.pData, 0, iter.current->data_size);
+            {
+                /* Initialize to zeros */
+                memset(iter->pData, 0, iter->pos->data_size);
+            }
         }
-        else if (PB_HTYPE(iter.current->type) == PB_HTYPE_ARRAY)
+    }
+    else if (PB_ATYPE(type) == PB_ATYPE_POINTER)
+    {
+        /* Initialize the pointer to NULL. */
+        *(void**)iter->pData = NULL;
+        
+        /* Initialize array count to 0. */
+        if (PB_HTYPE(type) == PB_HTYPE_REPEATED)
         {
-            *(size_t*)iter.pSize = 0;
+            *(pb_size_t*)iter->pSize = 0;
         }
-    } while (pb_field_next(&iter));
+    }
+    else if (PB_ATYPE(type) == PB_ATYPE_CALLBACK)
+    {
+        /* Don't overwrite callback */
+    }
+}
+
+static void pb_message_set_to_defaults(const pb_field_t fields[], void *dest_struct)
+{
+    pb_field_iter_t iter;
+
+    if (!pb_field_iter_begin(&iter, fields, dest_struct))
+        return; /* Empty message type */
+    
+    do
+    {
+        pb_field_set_to_default(&iter);
+    } while (pb_field_iter_next(&iter));
+}
+
+/*********************
+ * Decode all fields *
+ *********************/
+
+bool checkreturn pb_decode_noinit(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
+{
+    uint8_t fields_seen[(PB_MAX_REQUIRED_FIELDS + 7) / 8] = {0, 0, 0, 0, 0, 0, 0, 0};
+    uint32_t extension_range_start = 0;
+    pb_field_iter_t iter;
+    
+    /* Return value ignored, as empty message types will be correctly handled by
+     * pb_field_iter_find() anyway. */
+    (void)pb_field_iter_begin(&iter, fields, dest_struct);
     
     while (stream->bytes_left)
     {
-        uint32_t temp;
-        int tag, wire_type;
-        if (!pb_decode_varint32(stream, &temp))
-            return stream->bytes_left == 0; /* Was it EOF? */
-        
-        if (temp == 0)
-            return true; /* Special feature: allow 0-terminated messages. */
+        uint32_t tag;
+        pb_wire_type_t wire_type;
+        bool eof;
         
-        tag = temp >> 3;
-        wire_type = temp & 7;
+        if (!pb_decode_tag(stream, &wire_type, &tag, &eof))
+        {
+            if (eof)
+                break;
+            else
+                return false;
+        }
         
-        if (!pb_field_find(&iter, tag))
+        if (!pb_field_iter_find(&iter, tag))
         {
+            /* No match found, check if it matches an extension. */
+            if (tag >= extension_range_start)
+            {
+                if (!find_extension_field(&iter))
+                    extension_range_start = (uint32_t)-1;
+                else
+                    extension_range_start = iter.pos->tag;
+                
+                if (tag >= extension_range_start)
+                {
+                    size_t pos = stream->bytes_left;
+                
+                    if (!decode_extension(stream, tag, wire_type, &iter))
+                        return false;
+                    
+                    if (pos != stream->bytes_left)
+                    {
+                        /* The field was handled */
+                        continue;                    
+                    }
+                }
+            }
+        
             /* No match found, skip data */
-            skip(stream, wire_type);
+            if (!pb_skip_field(stream, wire_type))
+                return false;
             continue;
         }
         
-        fields_seen |= 1 << (iter.field_index & 31);
+        if (PB_HTYPE(iter.pos->type) == PB_HTYPE_REQUIRED
+            && iter.required_field_index < PB_MAX_REQUIRED_FIELDS)
+        {
+            fields_seen[iter.required_field_index >> 3] |= (uint8_t)(1 << (iter.required_field_index & 7));
+        }
             
         if (!decode_field(stream, wire_type, &iter))
             return false;
     }
     
-    /* Check that all required fields (mod 31) were present. */
-    for (i = 0; fields[i].tag != 0; i++)
+    /* Check that all required fields were present. */
     {
-        if (PB_HTYPE(fields[i].type) == PB_HTYPE_REQUIRED &&
-            !(fields_seen & (1 << (i & 31))))
+        /* First figure out the number of required fields by
+         * seeking to the end of the field array. Usually we
+         * are already close to end after decoding.
+         */
+        unsigned req_field_count;
+        pb_type_t last_type;
+        unsigned i;
+        do {
+            req_field_count = iter.required_field_index;
+            last_type = iter.pos->type;
+        } while (pb_field_iter_next(&iter));
+        
+        /* Fixup if last field was also required. */
+        if (PB_HTYPE(last_type) == PB_HTYPE_REQUIRED && iter.pos->tag != 0)
+            req_field_count++;
+        
+        /* Check the whole bytes */
+        for (i = 0; i < (req_field_count >> 3); i++)
         {
-            return false;
+            if (fields_seen[i] != 0xFF)
+                PB_RETURN_ERROR(stream, "missing required field");
         }
+        
+        /* Check the remaining bits */
+        if (fields_seen[req_field_count >> 3] != (0xFF >> (8 - (req_field_count & 7))))
+            PB_RETURN_ERROR(stream, "missing required field");
     }
     
     return true;
 }
 
-/* Field decoders */
-
-/* Copy destsize bytes from src so that values are casted properly.
- * On little endian machine, copy first n bytes of src
- * On big endian machine, copy last n bytes of src
- * srcsize must always be larger than destsize
- */
-static void endian_copy(void *dest, void *src, size_t destsize, size_t srcsize)
+bool checkreturn pb_decode(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
 {
-#ifdef __BIG_ENDIAN__
-    memcpy(dest, (char*)src + (srcsize - destsize), destsize);
-#else
-    memcpy(dest, src, destsize);
+    bool status;
+    pb_message_set_to_defaults(fields, dest_struct);
+    status = pb_decode_noinit(stream, fields, dest_struct);
+    
+#ifdef PB_ENABLE_MALLOC
+    if (!status)
+        pb_release(fields, dest_struct);
 #endif
+    
+    return status;
 }
 
-bool pb_dec_varint(pb_istream_t *stream, const pb_field_t *field, void *dest)
+bool pb_decode_delimited(pb_istream_t *stream, const pb_field_t fields[], void *dest_struct)
 {
-    uint64_t temp;
-    bool status = pb_decode_varint(stream, &temp);
-    endian_copy(dest, &temp, field->data_size, sizeof(temp));
+    pb_istream_t substream;
+    bool status;
+    
+    if (!pb_make_string_substream(stream, &substream))
+        return false;
+    
+    status = pb_decode(&substream, fields, dest_struct);
+    pb_close_string_substream(stream, &substream);
     return status;
 }
 
-bool pb_dec_svarint(pb_istream_t *stream, const pb_field_t *field, void *dest)
+#ifdef PB_ENABLE_MALLOC
+static void pb_release_single_field(const pb_field_iter_t *iter)
 {
-    uint64_t temp;
-    bool status = pb_decode_varint(stream, &temp);
-    temp = (temp >> 1) ^ -(int64_t)(temp & 1);
-    endian_copy(dest, &temp, field->data_size, sizeof(temp));
-    return status;
+    pb_type_t type;
+    type = iter->pos->type;
+
+    /* Release anything contained inside an extension or submsg.
+     * This has to be done even if the submsg itself is statically
+     * allocated. */
+    if (PB_LTYPE(type) == PB_LTYPE_EXTENSION)
+    {
+        /* Release fields from all extensions in the linked list */
+        pb_extension_t *ext = *(pb_extension_t**)iter->pData;
+        while (ext != NULL)
+        {
+            pb_field_iter_t ext_iter;
+            iter_from_extension(&ext_iter, ext);
+            pb_release_single_field(&ext_iter);
+            ext = ext->next;
+        }
+    }
+    else if (PB_LTYPE(type) == PB_LTYPE_SUBMESSAGE)
+    {
+        /* Release fields in submessage or submsg array */
+        void *pItem = iter->pData;
+        pb_size_t count = 1;
+        
+        if (PB_ATYPE(type) == PB_ATYPE_POINTER)
+        {
+            pItem = *(void**)iter->pData;
+        }
+        
+        if (PB_HTYPE(type) == PB_HTYPE_REPEATED)
+        {
+            count = *(pb_size_t*)iter->pSize;
+        }
+        
+        if (pItem)
+        {
+            while (count--)
+            {
+                pb_release((const pb_field_t*)iter->pos->ptr, pItem);
+                pItem = (uint8_t*)pItem + iter->pos->data_size;
+            }
+        }
+    }
+    
+    if (PB_ATYPE(type) == PB_ATYPE_POINTER)
+    {
+        if (PB_HTYPE(type) == PB_HTYPE_REPEATED &&
+            (PB_LTYPE(type) == PB_LTYPE_STRING ||
+             PB_LTYPE(type) == PB_LTYPE_BYTES))
+        {
+            /* Release entries in repeated string or bytes array */
+            void **pItem = *(void***)iter->pData;
+            pb_size_t count = *(pb_size_t*)iter->pSize;
+            while (count--)
+            {
+                pb_free(*pItem);
+                *pItem++ = NULL;
+            }
+        }
+        
+        if (PB_HTYPE(type) == PB_HTYPE_REPEATED)
+        {
+            /* We are going to release the array, so set the size to 0 */
+            *(pb_size_t*)iter->pSize = 0;
+        }
+        
+        /* Release main item */
+        pb_free(*(void**)iter->pData);
+        *(void**)iter->pData = NULL;
+    }
 }
 
-bool pb_dec_fixed(pb_istream_t *stream, const pb_field_t *field, void *dest)
+void pb_release(const pb_field_t fields[], void *dest_struct)
 {
-#ifdef __BIG_ENDIAN__
-    uint8_t bytes[8] = {0};
-    bool status = pb_read(stream, bytes, field->data_size);
-    uint8_t bebytes[8] = {bytes[7], bytes[6], bytes[5], bytes[4], 
-                          bytes[3], bytes[2], bytes[1], bytes[0]};
-    endian_copy(dest, lebytes, field->data_size, 8);
-    return status;
-#else
-    return pb_read(stream, (uint8_t*)dest, field->data_size);
+    pb_field_iter_t iter;
+    
+    if (!pb_field_iter_begin(&iter, fields, dest_struct))
+        return; /* Empty message type */
+    
+    do
+    {
+        pb_release_single_field(&iter);
+    } while (pb_field_iter_next(&iter));
+}
 #endif
+
+/* Field decoders */
+
+bool pb_decode_svarint(pb_istream_t *stream, int64_t *dest)
+{
+    uint64_t value;
+    if (!pb_decode_varint(stream, &value))
+        return false;
+    
+    if (value & 1)
+        *dest = (int64_t)(~(value >> 1));
+    else
+        *dest = (int64_t)(value >> 1);
+    
+    return true;
 }
 
-bool pb_dec_bytes(pb_istream_t *stream, const pb_field_t *field, void *dest)
+bool pb_decode_fixed32(pb_istream_t *stream, void *dest)
 {
-    pb_bytes_array_t *x = (pb_bytes_array_t*)dest;
+    #ifdef __BIG_ENDIAN__
+    uint8_t *bytes = (uint8_t*)dest;
+    uint8_t lebytes[4];
     
-    uint32_t temp;
-    if (!pb_decode_varint32(stream, &temp))
+    if (!pb_read(stream, lebytes, 4))
+        return false;
+    
+    bytes[0] = lebytes[3];
+    bytes[1] = lebytes[2];
+    bytes[2] = lebytes[1];
+    bytes[3] = lebytes[0];
+    return true;
+    #else
+    return pb_read(stream, (uint8_t*)dest, 4);
+    #endif   
+}
+
+bool pb_decode_fixed64(pb_istream_t *stream, void *dest)
+{
+    #ifdef __BIG_ENDIAN__
+    uint8_t *bytes = (uint8_t*)dest;
+    uint8_t lebytes[8];
+    
+    if (!pb_read(stream, lebytes, 8))
+        return false;
+    
+    bytes[0] = lebytes[7];
+    bytes[1] = lebytes[6];
+    bytes[2] = lebytes[5];
+    bytes[3] = lebytes[4];
+    bytes[4] = lebytes[3];
+    bytes[5] = lebytes[2];
+    bytes[6] = lebytes[1];
+    bytes[7] = lebytes[0];
+    return true;
+    #else
+    return pb_read(stream, (uint8_t*)dest, 8);
+    #endif   
+}
+
+static bool checkreturn pb_dec_varint(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    uint64_t value;
+    if (!pb_decode_varint(stream, &value))
+        return false;
+    
+    switch (field->data_size)
+    {
+        case 1: *(int8_t*)dest = (int8_t)value; break;
+        case 2: *(int16_t*)dest = (int16_t)value; break;
+        case 4: *(int32_t*)dest = (int32_t)value; break;
+        case 8: *(int64_t*)dest = (int64_t)value; break;
+        default: PB_RETURN_ERROR(stream, "invalid data_size");
+    }
+    
+    return true;
+}
+
+static bool checkreturn pb_dec_uvarint(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    uint64_t value;
+    if (!pb_decode_varint(stream, &value))
         return false;
-    x->size = temp;
     
-    /* Note: data_size includes the size of the x.size field, too.
-     * Calculate actual size starting from offset. */
-    if (x->size > field->data_size - offsetof(pb_bytes_array_t, bytes))
+    switch (field->data_size)
+    {
+        case 1: *(uint8_t*)dest = (uint8_t)value; break;
+        case 2: *(uint16_t*)dest = (uint16_t)value; break;
+        case 4: *(uint32_t*)dest = (uint32_t)value; break;
+        case 8: *(uint64_t*)dest = value; break;
+        default: PB_RETURN_ERROR(stream, "invalid data_size");
+    }
+    
+    return true;
+}
+
+static bool checkreturn pb_dec_svarint(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    int64_t value;
+    if (!pb_decode_svarint(stream, &value))
         return false;
     
-    return pb_read(stream, x->bytes, x->size);
+    switch (field->data_size)
+    {
+        case 1: *(int8_t*)dest = (int8_t)value; break;
+        case 2: *(int16_t*)dest = (int16_t)value; break;
+        case 4: *(int32_t*)dest = (int32_t)value; break;
+        case 8: *(int64_t*)dest = value; break;
+        default: PB_RETURN_ERROR(stream, "invalid data_size");
+    }
+    
+    return true;
 }
 
-bool pb_dec_string(pb_istream_t *stream, const pb_field_t *field, void *dest)
+static bool checkreturn pb_dec_fixed32(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    PB_UNUSED(field);
+    return pb_decode_fixed32(stream, dest);
+}
+
+static bool checkreturn pb_dec_fixed64(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    PB_UNUSED(field);
+    return pb_decode_fixed64(stream, dest);
+}
+
+static bool checkreturn pb_dec_bytes(pb_istream_t *stream, const pb_field_t *field, void *dest)
 {
     uint32_t size;
-    bool status;
+    size_t alloc_size;
+    pb_bytes_array_t *bdest;
+    
     if (!pb_decode_varint32(stream, &size))
         return false;
     
-    if (size > field->data_size - 1)
+    if (size > PB_SIZE_MAX)
+        PB_RETURN_ERROR(stream, "bytes overflow");
+    
+    alloc_size = PB_BYTES_ARRAY_T_ALLOCSIZE(size);
+    if (size > alloc_size)
+        PB_RETURN_ERROR(stream, "size too large");
+    
+    if (PB_ATYPE(field->type) == PB_ATYPE_POINTER)
+    {
+#ifndef PB_ENABLE_MALLOC
+        PB_RETURN_ERROR(stream, "no malloc support");
+#else
+        if (!allocate_field(stream, dest, alloc_size, 1))
+            return false;
+        bdest = *(pb_bytes_array_t**)dest;
+#endif
+    }
+    else
+    {
+        if (alloc_size > field->data_size)
+            PB_RETURN_ERROR(stream, "bytes overflow");
+        bdest = (pb_bytes_array_t*)dest;
+    }
+
+    bdest->size = (pb_size_t)size;
+    return pb_read(stream, bdest->bytes, size);
+}
+
+static bool checkreturn pb_dec_string(pb_istream_t *stream, const pb_field_t *field, void *dest)
+{
+    uint32_t size;
+    size_t alloc_size;
+    bool status;
+    if (!pb_decode_varint32(stream, &size))
         return false;
     
+    /* Space for null terminator */
+    alloc_size = size + 1;
+    
+    if (alloc_size < size)
+        PB_RETURN_ERROR(stream, "size too large");
+    
+    if (PB_ATYPE(field->type) == PB_ATYPE_POINTER)
+    {
+#ifndef PB_ENABLE_MALLOC
+        PB_RETURN_ERROR(stream, "no malloc support");
+#else
+        if (!allocate_field(stream, dest, alloc_size, 1))
+            return false;
+        dest = *(void**)dest;
+#endif
+    }
+    else
+    {
+        if (alloc_size > field->data_size)
+            PB_RETURN_ERROR(stream, "string overflow");
+    }
+    
     status = pb_read(stream, (uint8_t*)dest, size);
     *((uint8_t*)dest + size) = 0;
     return status;
 }
 
-bool pb_dec_submessage(pb_istream_t *stream, const pb_field_t *field, void *dest)
+static bool checkreturn pb_dec_submessage(pb_istream_t *stream, const pb_field_t *field, void *dest)
 {
+    bool status;
     pb_istream_t substream;
+    const pb_field_t* submsg_fields = (const pb_field_t*)field->ptr;
     
-    if (!make_string_substream(stream, &substream))
+    if (!pb_make_string_substream(stream, &substream))
         return false;
     
     if (field->ptr == NULL)
-        return false;
+        PB_RETURN_ERROR(stream, "invalid field descriptor");
+    
+    /* New array entries need to be initialized, while required and optional
+     * submessages have already been initialized in the top-level pb_decode. */
+    if (PB_HTYPE(field->type) == PB_HTYPE_REPEATED)
+        status = pb_decode(&substream, submsg_fields, dest);
+    else
+        status = pb_decode_noinit(&substream, submsg_fields, dest);
     
-    return pb_decode(&substream, (pb_field_t*)field->ptr, dest);
+    pb_close_string_substream(stream, &substream);
+    return status;
 }