-/* readwrite.c */
+/* readwrite.c */
#include "readwrite.h"
-#include <stdio.h>
-#include <stdint.h>
+#include <stdio.h> /* for FILE typedef*/
+#include <stdint.h> /* for uint16_t, uint32_t */
-extern uint16_t read_uint16_bigendian( FILE * file )
+
+
+/* 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);
+
+
+
+static uint8_t read_uintX_bigendian(FILE * file, uint32_t * x, uint8_t size)
{
- uint16_t x;
- x = (uint16_t) fgetc(file) << 8;
- x = x + (uint16_t) fgetc(file);
- return x;
+ 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;
+ int test;
+ for (; bitshift >= 0; bitshift = bitshift - 8)
+ {
+ test = fgetc(file);
+ if (EOF == test)
+ {
+ return 1;
+ }
+ * x = * x + ((uint32_t) test << bitshift);
+ }
+ return 0;
}
-extern uint32_t read_uint32_bigendian( FILE * file )
+
+
+static uint8_t write_uintX_bigendian(FILE * file, uint32_t x, uint8_t size)
{
- uint32_t x;
- x = (uint32_t) fgetc(file) << 24;
- x = x + ( (uint32_t) fgetc(file) << 16 );
- x = x + ( (uint32_t) fgetc(file) << 8 );
- x = x + (uint32_t) fgetc(file);
- return x;
+ 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)
+ {
+ if (EOF == fputc((x >> bitshift) & 0xFF, file))
+ {
+ return 1;
+ }
+ }
+ return 0;
}
-extern void write_uint16_bigendian( uint16_t x, FILE * file )
+
+
+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;
+ return err;
+}
+
+
+
+extern uint8_t read_uint16_bigendian(FILE * file, uint16_t * x)
{
- fputc( x >> 8, file );
- fputc( x & 0xFF, file );
+ /* See read_uint8() introductory comment for rationale. */
+ uint32_t y = * x;
+ uint8_t err = read_uintX_bigendian(file, &y, 16);
+ * x = (uint16_t) y;
+ return err;
}
-extern void write_uint32_bigendian( uint32_t x, FILE * file )
+
+
+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)
{
- fputc( x >> 24, file);
- fputc( ( x >> 16 ) & 0xFF, file);
- fputc( ( x >> 8 ) & 0xFF, file);
- fputc( x & 0xFF, file);
+ return write_uintX_bigendian(file, x, 32);
}