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);
+}