1 files changed, 61 insertions, 0 deletions
diff --git a/libs/bitfield-c/src/bitfield/8byte.c b/libs/bitfield-c/src/bitfield/8byte.c
new file mode 100644
index 0000000..9325ed1
--- /dev/null
+++ b/libs/bitfield-c/src/bitfield/8byte.c
@@ -0,0 +1,61 @@
+#include <bitfield/bitfield.h>
+#include <bitfield/8byte.h>
+#include <stddef.h>
+#include <limits.h>
+#include <string.h>
+
+#define EIGHTBYTE_BIT (8 * sizeof(uint64_t))
+
+uint8_t eightbyte_get_nibble(const uint64_t source, const uint8_t nibble_index,
+        const bool data_is_big_endian) {
+    return (uint8_t) eightbyte_get_bitfield(source, NIBBLE_SIZE * nibble_index,
+            NIBBLE_SIZE, data_is_big_endian);
+}
+
+uint8_t eightbyte_get_byte(uint64_t source, const uint8_t byte_index,
+        const bool data_is_big_endian) {
+    if(data_is_big_endian) {
+        source = __builtin_bswap64(source);
+    }
+    return (source >> (EIGHTBYTE_BIT - ((byte_index + 1) * CHAR_BIT))) & 0xFF;
+}
+
+// TODO is this funciton necessary anymore? is it any faster for uint64_t than
+// get_bitfield(data[], ...)? is the performance better on a 32 bit platform
+// like the PIC32?
+uint64_t eightbyte_get_bitfield(uint64_t source, const uint16_t offset,
+        const uint16_t bit_count, const bool data_is_big_endian) {
+    int startByte = offset / CHAR_BIT;
+    int endByte = (offset + bit_count - 1) / CHAR_BIT;
+
+    if(!data_is_big_endian) {
+        source = __builtin_bswap64(source);
+    }
+
+    uint8_t* bytes = (uint8_t*)&source;
+    uint64_t ret = bytes[startByte];
+    if(startByte != endByte) {
+        // The lowest byte address contains the most significant bit.
+        uint8_t i;
+        for(i = startByte + 1; i <= endByte; i++) {
+            ret = ret << 8;
+            ret = ret | bytes[i];
+        }
+    }
+
+    ret >>= 8 - find_end_bit(offset + bit_count);
+    return ret & bitmask(bit_count);
+}
+
+bool eightbyte_set_bitfield(uint64_t value, const uint16_t offset,
+        const uint16_t bit_count, uint64_t* destination) {
+    if(value > bitmask(bit_count)) {
+        return false;
+    }
+
+    int shiftDistance = EIGHTBYTE_BIT - offset - bit_count;
+    value <<= shiftDistance;
+    *destination &= ~(bitmask(bit_count) << shiftDistance);
+    *destination |= value;
+    return true;
+}