-#include <stdio.h>
-#include <limits.h>
-#include <stdint.h>
-#define UCHARSIZE (UCHAR_MAX + 1)
-
-uint16_t read_uint16_bigendian(FILE * file) {
-// Read uint16 from file in big-endian order.
- unsigned char a = fgetc(file);
- unsigned char b = fgetc(file);
- return (a * UCHARSIZE) + b; }
-
-void write_uint16_bigendian(uint16_t x, FILE * file) {
-// Write uint16 to file in beg-endian order.
- unsigned char a = x / UCHARSIZE;
- unsigned char b = x % UCHARSIZE;
- fputc(a, file);
- fputc(b, file); }
-
-uint32_t read_uint32_bigendian(FILE * file) {
-// Read uint32 from file in big-endian order.
- unsigned char a = fgetc(file);
- unsigned char b = fgetc(file);
- unsigned char c = fgetc(file);
- unsigned char d = fgetc(file);
- return (a * UCHARSIZE * UCHARSIZE * UCHARSIZE) + (b * UCHARSIZE * UCHARSIZE) + (c * UCHARSIZE) + d; }
-
-void write_uint32_bigendian(uint32_t x, FILE * file) {
-// Write uint32 to file in beg-endian order.
- unsigned char a = x / (UCHARSIZE * UCHARSIZE * UCHARSIZE);
- unsigned char b = (x - (a * UCHARSIZE * UCHARSIZE * UCHARSIZE)) / (UCHARSIZE * UCHARSIZE);
- unsigned char c = (x - ((a * UCHARSIZE * UCHARSIZE * UCHARSIZE) + (b * UCHARSIZE * UCHARSIZE))) / UCHARSIZE;
- unsigned char d = x % UCHARSIZE;
- fputc(a, file);
- fputc(b, file);
- fputc(c, file);
- fputc(d, file); }
+/* readwrite.c */
+
+#include "readwrite.h"
+#include <stdio.h> /* for FILE typedef*/
+#include <stdint.h> /* for uint16_t, uint32_t */
+
+
+
+/* Read/write "x" from/to "file" as bigendian representation of "size" bits. */
+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);
+
+
+
+static uint8_t read_uintX_bigendian(FILE * file, uint32_t * x, uint8_t size)
+{
+ if (0 != size % 8)
+ {
+ return 1;
+ }
+ int16_t bitshift = size - 8;
+
+ * x = 0;
+ int test;
+ for (; bitshift >= 0; bitshift = bitshift - 8)
+ {
+ test = fgetc(file);
+ if (EOF == test)
+ {
+ return 1;
+ }
+ * x = * x + ((uint32_t) test << bitshift);
+ }
+ return 0;
+}
+
+
+
+static uint8_t write_uintX_bigendian(FILE * file, uint32_t x, uint8_t size)
+{
+ if (0 != size % 8)
+ {
+ return 1;
+ }
+ int16_t bitshift = size - 8;
+
+ for (; bitshift >= 0; bitshift = bitshift - 8)
+ {
+ if (EOF == fputc((x >> bitshift) & 0xFF, file))
+ {
+ return 1;
+ }
+ }
+ return 0;
+}
+
+
+
+extern uint8_t read_uint8(FILE * file, uint8_t * x)
+{
+ uint32_t y = * x;
+ uint8_t fail = read_uintX_bigendian(file, &y, 8);
+ * x = (uint8_t) y;
+ return fail;
+}
+
+
+
+extern uint8_t read_uint16_bigendian(FILE * file, uint16_t * x)
+{
+ uint32_t y = * x;
+ uint8_t fail = read_uintX_bigendian(file, &y, 16);
+ * x = (uint16_t) y;
+ return fail;
+}
+
+
+
+extern uint8_t read_uint32_bigendian(FILE * file, uint32_t * x)
+{
+ return read_uintX_bigendian(file, x, 32);
+}
+
+
+
+extern uint8_t write_uint8(uint8_t x, FILE * file)
+{
+ return write_uintX_bigendian(file, x, 8);
+}
+
+
+
+extern uint8_t write_uint16_bigendian(uint16_t x, FILE * file)
+{
+ return write_uintX_bigendian(file, x, 16);
+}
+
+
+
+extern uint8_t write_uint32_bigendian(uint32_t x, FILE * file)
+{
+ return write_uintX_bigendian(file, x, 32);
+}