From 4c129f3bddc87508554227b961e382ee8ce3060f Mon Sep 17 00:00:00 2001
From: hkc <hatkidchan@gmail.com>
Date: Sun, 18 Sep 2022 16:21:18 +0300
Subject: [PATCH] Initial DD

---
 .gitignore       |  3 +++
 Makefile         | 13 +++++++++++++
 bitstream.c      | 44 ++++++++++++++++++++++++++++++++++++++++++++
 bitstream.h      | 25 +++++++++++++++++++++++++
 main.c           |  5 +++++
 test_bitstream.c | 22 ++++++++++++++++++++++
 6 files changed, 112 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 bitstream.c
 create mode 100644 bitstream.h
 create mode 100644 main.c
 create mode 100644 test_bitstream.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ace5795
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+test_bitstream
+main
+*.o
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..50d7851
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,13 @@
+OBJECTS := bitstream.o
+
+clean:
+	$(RM) *.o test_bitstream main
+
+run_%: %
+	./$^
+
+test_%: test_%.c $(OBJECTS)
+	$(CC) $^ -o $@
+
+%.o: %.c
+	$(CC) $^ -c -o $@
diff --git a/bitstream.c b/bitstream.c
new file mode 100644
index 0000000..2ef15ed
--- /dev/null
+++ b/bitstream.c
@@ -0,0 +1,44 @@
+#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;
+}
diff --git a/bitstream.h b/bitstream.h
new file mode 100644
index 0000000..b1633b1
--- /dev/null
+++ b/bitstream.h
@@ -0,0 +1,25 @@
+#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
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..00eb67c
--- /dev/null
+++ b/main.c
@@ -0,0 +1,5 @@
+// x-run: make clean all run
+#include "./bitstream.h"
+
+int main(void) {
+}
diff --git a/test_bitstream.c b/test_bitstream.c
new file mode 100644
index 0000000..a1ccdaf
--- /dev/null
+++ b/test_bitstream.c
@@ -0,0 +1,22 @@
+// 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);
+}