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diff --git a/pb_encode.h b/pb_encode.h
index 69b88e86..d9909fb0 100644
--- a/pb_encode.h
+++ b/pb_encode.h
@@ -1,36 +1,30 @@
-#ifndef _PB_ENCODE_H_
-#define _PB_ENCODE_H_
-
 /* pb_encode.h: Functions to encode protocol buffers. Depends on pb_encode.c.
- * The main function is pb_encode. You also need an output stream, structures
- * and their field descriptions (just like with pb_decode).
+ * The main function is pb_encode. You also need an output stream, and the
+ * field descriptions created by nanopb_generator.py.
  */
 
-#include <stdbool.h>
+#ifndef PB_ENCODE_H_INCLUDED
+#define PB_ENCODE_H_INCLUDED
+
 #include "pb.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-/* Lightweight output stream.
- * You can provide callback for writing or use pb_ostream_from_buffer.
- * 
- * Alternatively, callback can be NULL in which case the stream will just
- * count the number of bytes that would have been written. In this case
- * max_size is not checked.
+/* Structure for defining custom output streams. You will need to provide
+ * a callback function to write the bytes to your storage, which can be
+ * for example a file or a network socket.
+ *
+ * The callback must conform to these rules:
  *
- * Rules for callback:
  * 1) Return false on IO errors. This will cause encoding to abort.
- * 
  * 2) You can use state to store your own data (e.g. buffer pointer).
- * 
  * 3) pb_write will update bytes_written after your callback runs.
- * 
- * 4) Substreams will modify max_size and bytes_written. Don't use them to
- * calculate any pointers.
+ * 4) Substreams will modify max_size and bytes_written. Don't use them
+ *    to calculate any pointers.
  */
-struct _pb_ostream_t
+struct pb_ostream_s
 {
 #ifdef PB_BUFFER_ONLY
     /* Callback pointer is not used in buffer-only configuration.
@@ -41,33 +35,90 @@ struct _pb_ostream_t
      */
     int *callback;
 #else
-    bool (*callback)(pb_ostream_t *stream, const uint8_t *buf, size_t count);
+    bool (*callback)(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
+#endif
+    void *state;          /* Free field for use by callback implementation. */
+    size_t max_size;      /* Limit number of output bytes written (or use SIZE_MAX). */
+    size_t bytes_written; /* Number of bytes written so far. */
+    
+#ifndef PB_NO_ERRMSG
+    const char *errmsg;
 #endif
-    void *state; /* Free field for use by callback implementation */
-    size_t max_size; /* Limit number of output bytes written (or use SIZE_MAX). */
-    size_t bytes_written;
 };
 
-pb_ostream_t pb_ostream_from_buffer(uint8_t *buf, size_t bufsize);
-bool pb_write(pb_ostream_t *stream, const uint8_t *buf, size_t count);
+/***************************
+ * Main encoding functions *
+ ***************************/
 
-/* Encode struct to given output stream.
+/* Encode a single protocol buffers message from C structure into a stream.
  * Returns true on success, false on any failure.
  * The actual struct pointed to by src_struct must match the description in fields.
  * All required fields in the struct are assumed to have been filled in.
+ *
+ * Example usage:
+ *    MyMessage msg = {};
+ *    uint8_t buffer[64];
+ *    pb_ostream_t stream;
+ *
+ *    msg.field1 = 42;
+ *    stream = pb_ostream_from_buffer(buffer, sizeof(buffer));
+ *    pb_encode(&stream, MyMessage_fields, &msg);
  */
 bool pb_encode(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
 
-/* --- Helper functions ---
- * You may want to use these from your caller or callbacks.
+/* Same as pb_encode, but prepends the length of the message as a varint.
+ * Corresponds to writeDelimitedTo() in Google's protobuf API.
+ */
+bool pb_encode_delimited(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
+
+/* Encode the message to get the size of the encoded data, but do not store
+ * the data. */
+bool pb_get_encoded_size(size_t *size, const pb_field_t fields[], const void *src_struct);
+
+/**************************************
+ * Functions for manipulating streams *
+ **************************************/
+
+/* Create an output stream for writing into a memory buffer.
+ * The number of bytes written can be found in stream.bytes_written after
+ * encoding the message.
+ *
+ * Alternatively, you can use a custom stream that writes directly to e.g.
+ * a file or a network socket.
  */
+pb_ostream_t pb_ostream_from_buffer(pb_byte_t *buf, size_t bufsize);
 
-/* Encode field header based on LTYPE and field number defined in the field structure.
- * Call this from the callback before writing out field contents. */
+/* Pseudo-stream for measuring the size of a message without actually storing
+ * the encoded data.
+ * 
+ * Example usage:
+ *    MyMessage msg = {};
+ *    pb_ostream_t stream = PB_OSTREAM_SIZING;
+ *    pb_encode(&stream, MyMessage_fields, &msg);
+ *    printf("Message size is %d\n", stream.bytes_written);
+ */
+#ifndef PB_NO_ERRMSG
+#define PB_OSTREAM_SIZING {0,0,0,0,0}
+#else
+#define PB_OSTREAM_SIZING {0,0,0,0}
+#endif
+
+/* Function to write into a pb_ostream_t stream. You can use this if you need
+ * to append or prepend some custom headers to the message.
+ */
+bool pb_write(pb_ostream_t *stream, const pb_byte_t *buf, size_t count);
+
+
+/************************************************
+ * Helper functions for writing field callbacks *
+ ************************************************/
+
+/* Encode field header based on type and field number defined in the field
+ * structure. Call this from the callback before writing out field contents. */
 bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field);
 
-/* Encode field header by manually specifing wire type. You need to use this if
- * you want to write out packed arrays from a callback field. */
+/* Encode field header by manually specifing wire type. You need to use this
+ * if you want to write out packed arrays from a callback field. */
 bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, uint32_t field_number);
 
 /* Encode an integer in the varint format.
@@ -79,7 +130,7 @@ bool pb_encode_varint(pb_ostream_t *stream, uint64_t value);
 bool pb_encode_svarint(pb_ostream_t *stream, int64_t value);
 
 /* Encode a string or bytes type field. For strings, pass strlen(s) as size. */
-bool pb_encode_string(pb_ostream_t *stream, const uint8_t *buffer, size_t size);
+bool pb_encode_string(pb_ostream_t *stream, const pb_byte_t *buffer, size_t size);
 
 /* Encode a fixed32, sfixed32 or float value.
  * You need to pass a pointer to a 4-byte wide C variable. */
@@ -90,29 +141,12 @@ bool pb_encode_fixed32(pb_ostream_t *stream, const void *value);
 bool pb_encode_fixed64(pb_ostream_t *stream, const void *value);
 
 /* Encode a submessage field.
- * You need to pass the pb_field_t array and pointer to struct, just like with pb_encode().
- * This internally encodes the submessage twice, first to calculate message size and then to actually write it out.
+ * You need to pass the pb_field_t array and pointer to struct, just like
+ * with pb_encode(). This internally encodes the submessage twice, first to
+ * calculate message size and then to actually write it out.
  */
 bool pb_encode_submessage(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);
 
-/* --- Internal functions ---
- * These functions are not terribly useful for the average library user, but
- * are exported to make the unit testing and extending nanopb easier.
- */
-
-#ifdef NANOPB_INTERNALS
-bool pb_enc_varint(pb_ostream_t *stream, const pb_field_t *field, const void *src);
-bool pb_enc_svarint(pb_ostream_t *stream, const pb_field_t *field, const void *src);
-bool pb_enc_fixed32(pb_ostream_t *stream, const pb_field_t *field, const void *src);
-bool pb_enc_fixed64(pb_ostream_t *stream, const pb_field_t *field, const void *src);
-bool pb_enc_bytes(pb_ostream_t *stream, const pb_field_t *field, const void *src);
-bool pb_enc_string(pb_ostream_t *stream, const pb_field_t *field, const void *src);
-#endif
-
-/* This function is not recommended for new programs. Use pb_encode_submessage()
- * instead, it has the same functionality with a less confusing interface. */
-bool pb_enc_submessage(pb_ostream_t *stream, const pb_field_t *field, const void *src);
-
 #ifdef __cplusplus
 } /* extern "C" */
 #endif