4 files changed, 47 insertions, 8 deletions

diff --git a/src/bitfield/8byte.c b/src/bitfield/8byte.c
index 72f7e32b..0ae6894b 100644
--- a/src/bitfield/8byte.c
+++ b/src/bitfield/8byte.c
@@ -47,8 +47,8 @@ uint64_t eightbyte_get_bitfield(uint64_t source, const uint16_t offset,
     return ret & bitmask(bit_count);
 }
 
-bool eightbyte_set_bitfield(uint64_t* destination, uint64_t value, const uint16_t offset,
-        const uint16_t 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;
     }
diff --git a/src/bitfield/8byte.h b/src/bitfield/8byte.h
index 2916c218..04512690 100644
--- a/src/bitfield/8byte.h
+++ b/src/bitfield/8byte.h
@@ -74,8 +74,8 @@ uint8_t eightbyte_get_byte(const uint64_t source, const uint8_t byte_index,
  * Returns true if the bit_count is enough to fully represent the value, and
  *      false if it will not fit.
  */
-bool eightbyte_set_bitfield(uint64_t* destination, uint64_t value,
-        const uint16_t offset, const uint16_t bit_count);
+bool eightbyte_set_bitfield(uint64_t value,
+        const uint16_t offset, const uint16_t bit_count, uint64_t* destination);
 
 /* Private: Determine the index of the last bit used.
  */
diff --git a/src/bitfield/bitfield.c b/src/bitfield/bitfield.c
index e40ab1ab..b244c9b1 100644
--- a/src/bitfield/bitfield.c
+++ b/src/bitfield/bitfield.c
@@ -34,10 +34,7 @@ uint64_t get_bitfield(const uint8_t source[], const uint8_t source_length,
         return 0;
     }
 
-    union {
-        uint64_t whole;
-        uint8_t bytes[sizeof(uint64_t)];
-    } combined;
+    ArrayOrBytes combined;
     memset(combined.bytes, 0, sizeof(combined.bytes));
     copy_bits_right_aligned(source, source_length, offset, bit_count,
             combined.bytes, sizeof(combined.bytes));
@@ -53,3 +50,22 @@ bool set_nibble(const uint16_t nibble_index, const uint8_t value,
             destination_length, nibble_index * NIBBLE_SIZE);
 }
 
+bool set_bitfield(const uint64_t value, const uint16_t offset,
+        const uint16_t bit_count, uint8_t destination[],
+        uint16_t destination_length) {
+    if(value > bitmask(bit_count)) {
+        return false;
+    }
+
+    ArrayOrBytes combined = {
+        whole: value
+    };
+
+    if(BYTE_ORDER == LITTLE_ENDIAN) {
+        combined.whole = __builtin_bswap64(combined.whole);
+    }
+
+    return copy_bits(combined.bytes, sizeof(combined.bytes),
+            sizeof(combined.bytes) * CHAR_BIT - bit_count, bit_count,
+            destination, destination_length, offset);
+}
diff --git a/src/bitfield/bitfield.h b/src/bitfield/bitfield.h
index a080c866..b3c30f02 100644
--- a/src/bitfield/bitfield.h
+++ b/src/bitfield/bitfield.h
@@ -168,6 +168,22 @@ bool copy_bytes_right_aligned(const uint8_t source[], const uint16_t source_leng
 bool set_nibble(const uint16_t nibble_index, const uint8_t value,
                 uint8_t* destination, const uint16_t destination_length);
 
+/* Public: Set the bit field in the given data array to the new value.
+ *
+ * value - the value to set in the bit field.
+ * offset - the starting index of the bit field (beginning from 0).
+ * bit_count - the number of bits to set in the data.
+ * destination - the destination array.
+ * destination_length - the total length of the destination array in bytes,
+ *      for range checking.
+ *
+ * Returns true if the bit_count is enough to fully represent the value, and
+ *      false if it will not fit.
+ */
+bool set_bitfield(const uint64_t value, const uint16_t offset,
+        const uint16_t bit_count, uint8_t destination[],
+        uint16_t destination_length);
+
 /* Private:
  */
 uint16_t bits_to_bytes(uint32_t bits);
@@ -178,6 +194,13 @@ uint16_t bits_to_bytes(uint32_t bits);
  */
 uint64_t bitmask(const uint8_t bit_count);
 
+/* Private: A union to assist swapping between uint64_t and a uint8_t array.
+ */
+typedef union {
+    uint64_t whole;
+    uint8_t bytes[sizeof(uint64_t)];
+} ArrayOrBytes;
+
 #ifdef __cplusplus
 }
 #endif