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-rw-r--r--libs/bitfield-c/src/bitfield/bitarray.c145
1 files changed, 145 insertions, 0 deletions
diff --git a/libs/bitfield-c/src/bitfield/bitarray.c b/libs/bitfield-c/src/bitfield/bitarray.c
new file mode 100644
index 0000000..dcb9a08
--- /dev/null
+++ b/libs/bitfield-c/src/bitfield/bitarray.c
@@ -0,0 +1,145 @@
+#include <bitfield/bitfield.h>
+#include <stddef.h>
+#include <limits.h>
+#include <string.h>
+
+#define PREPARE_FIRST_COPY() \
+ do { \
+ if (bit_count >= (CHAR_BIT - destination_offset_modulo)) { \
+ *destination &= reverse_mask[destination_offset_modulo]; \
+ bit_count -= CHAR_BIT - destination_offset_modulo; \
+ } else { \
+ *destination &= reverse_mask[destination_offset_modulo] \
+ | reverse_mask_xor[destination_offset_modulo + bit_count + 1];\
+ c &= reverse_mask[destination_offset_modulo + bit_count ];\
+ bit_count = 0; \
+ } } while (0)
+
+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 };
+
+bool copy_bits(const uint8_t* source_origin, const uint16_t source_length,
+ const uint16_t source_offset, uint16_t bit_count,
+ uint8_t* destination_origin, const uint16_t destination_length,
+ const uint16_t destination_offset) {
+ if(bit_count < 1) {
+ return false;
+ }
+
+ if(source_offset + bit_count > source_length * CHAR_BIT ||
+ destination_offset + bit_count > destination_length * CHAR_BIT ) {
+ return false;
+ }
+
+ const uint8_t* source = source_origin + (source_offset / CHAR_BIT);
+ uint8_t* destination = destination_origin + (destination_offset / CHAR_BIT);
+ int source_offset_modulo = source_offset % CHAR_BIT;
+ int destination_offset_modulo = destination_offset % CHAR_BIT;
+
+ if(source_offset_modulo == destination_offset_modulo) {
+ if(source_offset_modulo > 0) {
+ uint8_t c = reverse_mask_xor[destination_offset_modulo] & *source++;
+ PREPARE_FIRST_COPY();
+ *destination++ |= c;
+ }
+
+ int byte_len = bit_count / CHAR_BIT;
+ int bit_count_modulo = bit_count % CHAR_BIT;
+
+ if(byte_len > 0) {
+ memcpy(destination, source, byte_len);
+ source += byte_len;
+ destination += byte_len;
+ }
+
+ if(bit_count_modulo > 0) {
+ *destination &= reverse_mask_xor[bit_count_modulo];
+ *destination |= reverse_mask[bit_count_modulo] & *source;
+ }
+ } else {
+ int bit_diff_left_shift;
+ int bit_diff_right_shift;
+ uint8_t c;
+ /*
+ * Begin: Line things up on destination.
+ */
+ if(source_offset_modulo > destination_offset_modulo) {
+ bit_diff_left_shift = source_offset_modulo - destination_offset_modulo;
+ bit_diff_right_shift = CHAR_BIT - bit_diff_left_shift;
+
+ c = *source++ << bit_diff_left_shift;
+ c |= *source >> bit_diff_right_shift;
+ c &= reverse_mask_xor[destination_offset_modulo];
+ } else {
+ bit_diff_right_shift = destination_offset_modulo - source_offset_modulo;
+ bit_diff_left_shift = CHAR_BIT - bit_diff_right_shift;
+
+ c = *source >> bit_diff_right_shift &
+ reverse_mask_xor[destination_offset_modulo];
+ }
+ PREPARE_FIRST_COPY();
+ *destination++ |= c;
+
+ /*
+ * Middle: copy with only shifting the source.
+ */
+ int byte_len = bit_count / CHAR_BIT;
+ while(--byte_len >= 0) {
+ c = *source++ << bit_diff_left_shift;
+ c |= *source >> bit_diff_right_shift;
+ *destination++ = c;
+ }
+
+ /*
+ * End: copy the remaing bits;
+ */
+ int bit_count_modulo = bit_count % CHAR_BIT;
+ if(bit_count_modulo > 0) {
+ c = *source++ << bit_diff_left_shift;
+ c |= *source >> bit_diff_right_shift;
+ c &= reverse_mask[bit_count_modulo];
+
+ *destination &= reverse_mask_xor[bit_count_modulo];
+ *destination |= c;
+ }
+ }
+ return true;
+}
+
+uint16_t bits_to_bytes(uint32_t bits) {
+ uint8_t byte_count = bits / CHAR_BIT;
+ if(bits % CHAR_BIT != 0) {
+ ++byte_count;
+ }
+ return byte_count;
+}
+
+/**
+ * Find the ending bit of a bitfield within the final byte.
+ *
+ * Returns: a bit position from 0 to 7.
+ */
+uint8_t find_end_bit(const uint16_t numBits) {
+ int endBit = numBits % CHAR_BIT;
+ return endBit == 0 ? CHAR_BIT : endBit;
+}
+
+bool copy_bits_right_aligned(const uint8_t source[], const uint16_t source_length,
+ const uint16_t offset, const uint16_t bit_count,
+ uint8_t* destination, const uint16_t destination_length) {
+ return copy_bits(source, source_length, offset, bit_count, destination,
+ destination_length,
+ // provide a proper destination offset so the result is right
+ // aligned
+ (destination_length - bits_to_bytes(bit_count)) * CHAR_BIT +
+ CHAR_BIT - find_end_bit(bit_count));
+}
+
+bool copy_bytes_right_aligned(const uint8_t source[], const uint16_t source_length,
+ const uint16_t offset, const uint16_t byte_count,
+ uint8_t* destination, const uint16_t destination_length) {
+ return copy_bits_right_aligned(source, source_length, offset * CHAR_BIT,
+ byte_count * CHAR_BIT, destination, destination_length);
+}