Check if a value will fit in bitfield before setting.

2 files changed, 10 insertions, 6 deletions

diff --git a/src/bitfield/8byte.c b/src/bitfield/8byte.c
index 77251996..3b6b5466 100644
--- a/src/bitfield/8byte.c
+++ b/src/bitfield/8byte.c
@@ -40,16 +40,17 @@ uint64_t get_bit_field(uint64_t source, const uint16_t startBit,
     return int_result;
 }
 
-/**
- * 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 set_bit_field(uint64_t* destination, uint64_t value, const uint16_t offset,
+bool set_bit_field(uint64_t* destination, uint64_t value, const uint16_t offset,
         const uint16_t bit_count) {
+    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;
 }
 
 uint8_t nth_byte(const uint64_t source, const uint16_t byte_index) {
diff --git a/src/bitfield/8byte.h b/src/bitfield/8byte.h
index 9cbf61a9..36b5fe60 100644
--- a/src/bitfield/8byte.h
+++ b/src/bitfield/8byte.h
@@ -55,8 +55,11 @@ uint64_t get_bit_field(uint64_t source, const uint16_t offset,
  * 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.
+ *
+ * Returns true if the bit_count is enough to fully represent the value, and
+ *      false if it will not fit.
  */
-void set_bit_field(uint64_t* destination, uint64_t value, const uint16_t offset,
+bool set_bit_field(uint64_t* destination, uint64_t value, const uint16_t offset,
         const uint16_t bit_count);
 
 /* Public: Retreive the nth byte out of 8 bytes in a uint64_t.