#include <limits.h>
#include <string.h>
#include <stddef.h>
+#include <endian.h>
-#define NIBBLE_SIZE (CHAR_BIT / 2)
-
-#define PREPARE_FIRST_COPY() \
- do { \
- if (source_length >= (CHAR_BIT - destination_offset_modulo)) { \
- *destination &= reverse_mask[destination_offset_modulo]; \
- source_length -= CHAR_BIT - destination_offset_modulo; \
- } else { \
- *destination &= reverse_mask[destination_offset_modulo] \
- | reverse_mask_xor[destination_offset_modulo + source_length + 1];\
- c &= reverse_mask[destination_offset_modulo + source_length ];\
- source_length = 0; \
- } } while (0)
-
-/**
- * Find the ending bit of a bitfield within the final byte.
- *
- * Returns: a bit position from 0 to 7.
- */
-static uint8_t findEndBit(const uint16_t startBit, const uint16_t numBits) {
- int endBit = (startBit + numBits) % CHAR_BIT;
- return endBit == 0 ? CHAR_BIT : endBit;
-}
-
-
-// TODO can probably remove this
-static int byteForBit(const uint16_t startBit) {
- return startBit / CHAR_BIT;
-}
-
-/* Thanks to
- * http://stackoverflow.com/questions/3534535/whats-a-time-efficient-algorithm-to-copy-unaligned-bit-arrays
- */
-static void bitarray_copy(const uint8_t* source_origin, int source_offset,
- int source_length, uint8_t* destination_origin, int destination_offset) {
- static const uint8_t mask[] =
- { 0x55, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff };
- static const uint8_t reverse_mask[] =
- { 0x55, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe, 0xff };
- static const uint8_t reverse_mask_xor[] =
- { 0xff, 0x7f, 0x3f, 0x1f, 0x0f, 0x07, 0x03, 0x01, 0x00 };
-
- if(source_length < 1) {
- return;
- }
-
- int source_offset_modulo;
- int destination_offset_modulo;
-
- const uint8_t* source = source_origin + byteForBit(source_offset);
- uint8_t* destination = destination_origin + byteForBit(destination_offset);
-
- source_offset_modulo = source_offset % CHAR_BIT;
- destination_offset_modulo = destination_offset % CHAR_BIT;
-
- if(source_offset_modulo == destination_offset_modulo) {
- if(source_offset_modulo) {
- uint8_t c;
-
- c = reverse_mask_xor[destination_offset_modulo] & *source++;
-
- PREPARE_FIRST_COPY();
- *destination++ |= c;
- }
-
- int byte_len = source_length / CHAR_BIT;
- int source_length_modulo = source_length % CHAR_BIT;
-
- if(byte_len) {
- memcpy(destination, source, byte_len);
- source += byte_len;
- destination += byte_len;
- }
- if(source_length_modulo) {
- *destination &= reverse_mask_xor[source_length_modulo];
- *destination |= reverse_mask[source_length_modulo] & *source;
- }
- } else {
- int bit_diff_ls;
- int bit_diff_rs;
- uint8_t c;
- /*
- * Begin: Line things up on destination.
- */
- if (source_offset_modulo > destination_offset_modulo) {
- bit_diff_ls = source_offset_modulo - destination_offset_modulo;
- bit_diff_rs = CHAR_BIT - bit_diff_ls;
-
- c = *source++ << bit_diff_ls;
- c |= *source >> bit_diff_rs;
- c &= reverse_mask_xor[destination_offset_modulo];
- } else {
- bit_diff_rs = destination_offset_modulo - source_offset_modulo;
- bit_diff_ls = CHAR_BIT - bit_diff_rs;
-
- c = *source >> bit_diff_rs &
- reverse_mask_xor[destination_offset_modulo];
- }
- PREPARE_FIRST_COPY();
- *destination++ |= c;
-
- /*
- * Middle: copy with only shifting the source.
- */
- int byte_len = source_length / CHAR_BIT;
-
- while(--byte_len >= 0) {
- c = *source++ << bit_diff_ls;
- c |= *source >> bit_diff_rs;
- *destination++ = c;
- }
-
- /*
- * End: copy the remaing bits;
- */
- int source_length_modulo = source_length % CHAR_BIT;
- if(source_length_modulo) {
- c = *source++ << bit_diff_ls;
- c |= *source >> bit_diff_rs;
- c &= reverse_mask[source_length_modulo];
-
- *destination &= reverse_mask_xor[source_length_modulo];
- *destination |= c;
- }
- }
-}
-
-uint64_t bitmask(const uint8_t numBits) {
- return (((uint64_t)0x1) << numBits) - 1;
-}
-
-uint64_t getBitField(uint64_t data, const uint16_t startBit,
- const uint16_t numBits, bool bigEndian) {
- uint64_t result;
- getBits(startBit, numBits, (const uint8_t*)&data,
- CHAR_BIT * sizeof(uint64_t),
- bigEndian ? ENDIANNESS_BIG_ENDIAN : ENDIANNESS_LITTLE_ENDIAN,
- &result);
- return result;
+uint64_t bitmask(const uint8_t bit_count) {
+ return (((uint64_t)0x1) << bit_count) - 1;
}
-/**
- * TODO it would be nice to have a warning if you call with this a value that
- * won't fit in the number of bits you've specified it should use.
- */
-void setBitField(uint64_t* data, uint64_t value, int startBit, int numBits) {
- int shiftDistance = 64 - startBit - numBits;
- value <<= shiftDistance;
- *data &= ~(bitmask(numBits) << shiftDistance);
- *data |= value;
-}
-
-uint8_t nthByte(uint64_t source, int byteNum) {
- return (source >> (64 - ((byteNum + 1) * CHAR_BIT))) & 0xFF;
-}
-
-uint8_t getNibble(const uint8_t nibble_index, const uint8_t data[],
- const uint8_t length, Endianness endianness) {
+uint8_t get_nibble(const uint8_t source[], const uint8_t source_length,
+ const uint8_t nibble_index) {
uint8_t byte_index = nibble_index / 2;
- uint8_t result;
- if(byte_index < length) {
- result = data[byte_index];
- if(nibble_index % 2 == 0) {
- result >>= NIBBLE_SIZE;
- }
+ uint8_t result = get_byte(source, source_length, byte_index);
+ if(nibble_index % 2 == 0) {
+ result >>= NIBBLE_SIZE;
}
result &= bitmask(NIBBLE_SIZE);
return result;
}
-// TODO getBytes, return status and store in output parameter
-uint8_t getByte(const uint8_t byte_index, const uint8_t data[],
- const uint8_t length, Endianness endianness) {
- if(byte_index < length) {
- return data[byte_index];
+uint8_t get_byte(const uint8_t source[], const uint8_t source_length,
+ const uint8_t byte_index) {
+ if(byte_index < source_length) {
+ return source[byte_index];
}
return 0;
}
-void getBits(const uint16_t start_index, const uint16_t field_size,
- const uint8_t data[], const uint8_t length, Endianness endianness,
- uint8_t* result) {
- bitarray_copy(data, start_index, field_size, result, 0);
+uint64_t get_bitfield(const uint8_t source[], const uint8_t source_length,
+ const uint16_t offset, const uint16_t bit_count) {
+ if(bit_count > 64 || bit_count < 1) {
+ // TODO error reporting?
+ return 0;
+ }
+
+ union {
+ uint64_t whole;
+ uint8_t bytes[sizeof(uint64_t)];
+ } combined;
+ copy_bits_right_aligned(source, source_length, offset, bit_count,
+ combined.bytes, sizeof(combined.bytes));
+ return htobe64(combined.whole);
+}
+
+bool set_nibble(const uint16_t nibble_index, const uint8_t value,
+ uint8_t* destination, const uint16_t destination_length) {
+ return copy_bits(&value, CHAR_BIT, NIBBLE_SIZE, NIBBLE_SIZE, destination,
+ destination_length, nibble_index * NIBBLE_SIZE);
}
+
Code Review / apps / agl-service-can-low-level.git / blobdiff