X-Git-Url: https://plomlompom.com/repos/foo.html?a=blobdiff_plain;ds=sidebyside;f=src%2Freadwrite.c;h=da5f73fd962dda486b0dc832d9addd365ac91903;hb=6ba18516a602b3d4ad95981887ad9c5eb40a335a;hp=039dadea4a6855e1f2222241193897db4f987b4c;hpb=4d9b6ac142740aa337fc3e622902c9595c36f6d0;p=plomrogue
diff --git a/src/readwrite.c b/src/readwrite.c
index 039dade..da5f73f 100644
--- a/src/readwrite.c
+++ b/src/readwrite.c
@@ -2,11 +2,19 @@
#include "readwrite.h"
#include /* for FILE typedef*/
-#include /* for uint16_t, uint32_t */
+#include /* for uint8_t, uint16_t, uint32_t */
-/* Read/write "x" from/to "file" as bigendian representation of "size" bits. */
+/* Read/write "x" from/to "file" as bigendian representation of "size" bits.
+ * Only multiples of 8 allowed for "size". On failure, return 1, else 0.
+ *
+ * As of of now, all other read/write functions build on top of these. TODO:
+ * Consider externing these so-far internal functions and dropping the
+ * interfaces to them, instead relying on their internal validity checks.
+ * (Usage of padded memory copies instead of directly manipulating * x as is
+ * done in read_uint* would need to be added, though.)
+ */
static uint8_t read_uintX_bigendian(FILE * file, uint32_t * x, uint8_t size);
static uint8_t write_uintX_bigendian(FILE * file, uint32_t x, uint8_t size);
@@ -14,10 +22,10 @@ static uint8_t write_uintX_bigendian(FILE * file, uint32_t x, uint8_t size);
static uint8_t read_uintX_bigendian(FILE * file, uint32_t * x, uint8_t size)
{
- if (0 != size % 8)
- {
- return 1;
- }
+ if (0 != size % 8) /* This bit number validity check is redundant */
+ { /* as long as this function is only available */
+ return 1; /* through extern interfaces pre-defining the */
+ } /* bit number. TODO: Consider dropping it. */
int16_t bitshift = size - 8;
* x = 0;
@@ -38,10 +46,10 @@ static uint8_t read_uintX_bigendian(FILE * file, uint32_t * x, uint8_t size)
static uint8_t write_uintX_bigendian(FILE * file, uint32_t x, uint8_t size)
{
- if (0 != size % 8)
- {
- return 1;
- }
+ if (0 != size % 8) /* See comment */
+ { /* on identical */
+ return 1; /* code block in */
+ } /* read_uintX_bigendian(). */
int16_t bitshift = size - 8;
for (; bitshift >= 0; bitshift = bitshift - 8)
@@ -58,6 +66,9 @@ static uint8_t write_uintX_bigendian(FILE * file, uint32_t x, uint8_t size)
extern uint8_t read_uint8(FILE * file, uint8_t * x)
{
+ /* Since read_uintX_bigendian() works on -- and zeroes -- four bytes, direct
+ * work on values of fewer bytes would corrupt immediate neighbor values.
+ */
uint32_t y = * x;
uint8_t err = read_uintX_bigendian(file, &y, 8);
* x = (uint8_t) y;
@@ -68,6 +79,7 @@ extern uint8_t read_uint8(FILE * file, uint8_t * x)
extern uint8_t read_uint16_bigendian(FILE * file, uint16_t * x)
{
+ /* See read_uint8() introductory comment for rationale. */
uint32_t y = * x;
uint8_t err = read_uintX_bigendian(file, &y, 16);
* x = (uint16_t) y;