Initial DD

.gitignore

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+test_bitstream
+main
+*.o

Makefile

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+OBJECTS := bitstream.o
+
+clean:
+	$(RM) *.o test_bitstream main
+
+run_%: %
+	./$^
+
+test_%: test_%.c $(OBJECTS)
+	$(CC) $^ -o $@
+
+%.o: %.c
+	$(CC) $^ -c -o $@

bitstream.c

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+#include "./bitstream.h"
+#include <stdio.h>
+
+BitStream bitstream_load_from_file(FILE *fp) {
+  fseek(fp, SEEK_END, 0);
+  size_t length = ftell(fp);
+  fseek(fp, SEEK_SET, 0);
+  BitStream bs = bitstream_init_empty(length);
+  fread(bs.buffer, 1, length, fp);
+  return bs;
+}
+
+BitStream bitstream_init_empty(size_t size_in_bytes) {
+  return (BitStream){
+    .buffer = malloc(size_in_bytes),
+    .buffer_size = size_in_bytes,
+    .offset = 0
+  };
+}
+
+bool bitstream_end(BitStream bs) {
+  return (bs.offset >> 3) >= bs.buffer_size;
+}
+
+uint8_t bitstream_get(BitStream bs, off_t offset) {
+  return bs.buffer[offset >> 3] & (0x80 >> (offset & 7)) ? 1 : 0;
+}
+
+
+uint8_t bitstream_next(BitStream *bs) {
+  uint8_t val = bitstream_get(*bs, bs->offset);
+  bs->offset++;
+  return val;
+}
+
+void bitstream_set(BitStream bs, off_t offset, uint8_t value) {
+  bs.buffer[offset >> 3] &= ~(0x80 >> (offset & 7));
+  bs.buffer[offset >> 3] |= (value ? 1 : 0) * (0x80 >> (offset & 7));
+}
+
+void bitstream_unload(BitStream *bs) {
+  free(bs->buffer);
+  bs->buffer = 0;
+}

bitstream.h

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+#ifndef _BITSTREAM_H_
+#define _BITSTREAM_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdbool.h>
+
+typedef struct bit_stream {
+    uint8_t *buffer;
+    size_t buffer_size;
+    off_t offset;
+} BitStream;
+
+BitStream bitstream_load_from_file(FILE *fp);
+BitStream bitstream_init_empty(size_t size_in_bytes);
+
+uint8_t bitstream_get(BitStream bs, off_t offset);
+uint8_t bitstream_next(BitStream *bs);
+bool bitstream_end(BitStream bs);
+void bitstream_set(BitStream bs, off_t offset, uint8_t value);
+
+void bitstream_unload(BitStream *bs);
+
+#endif

main.c

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+// x-run: make clean all run
+#include "./bitstream.h"
+
+int main(void) {
+}

test_bitstream.c

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+// x-run: make clean test_bitstream run_test_bitstream
+#include "./bitstream.h"
+
+int main(void) {
+  BitStream bs = bitstream_init_empty(16 * 2);
+  bitstream_set(bs, 16 * 0 + 0, 1);
+  bitstream_set(bs, 16 * 2 + 2, 1);
+  bitstream_set(bs, 16 * 4 + 4, 1);
+  bitstream_set(bs, 16 * 8 + 8, 1);
+  bitstream_set(bs, 16 * 4 + 4, 0);
+  printf("  ");
+  for (int i = 0; i < 16; i++) printf("%2x", i);
+  printf("\n");
+  for (int i = 0; !bitstream_end(bs); i++) {
+    if (i % 16 == 0) printf("%2x", i >> 4);
+    printf("\033[%dm  ", bitstream_next(&bs) \
+        ? (i >> 4 & 1 ? 47 : 107) \
+        : (i >> 4 & 1 ? 40 : 100));
+    if (i % 16 == 15) printf("\033[0m\n");
+  }
+  bitstream_unload(&bs);
+}