add bit reader module

Author: fsasm

bit_reader.c

@@ -0,0 +1,80 @@
+/*
+ * @file bit_reader.c
+ * @author Fabjan Sukalia <[email protected]>
+ * @date 2016-02-03
+ */
+
+#include <stdlib.h>
+#include <assert.h>
+#include "bit_reader.h"
+
+struct bit_reader {
+	FILE *file;
+	uint8_t buffer;
+	uint8_t bit_pos;
+};
+
+struct bit_reader *bit_reader_create(FILE *in)
+{
+	struct bit_reader *reader = calloc(1, sizeof(*reader));
+	reader->file = in;
+	return reader;
+}
+
+void bit_reader_destroy(struct bit_reader *reader)
+{
+	free(reader);
+}
+
+bool bit_reader_next_bit(struct bit_reader *reader, uint8_t *bit)
+{
+	assert(reader != NULL);
+	assert(bit    != NULL);
+
+	if (reader->bit_pos == 0) {
+		/* read next byte */
+		uint8_t data;
+		if (fread(&data, sizeof(data), 1, reader->file) != sizeof(data))
+			return false;
+
+		if (data == 0xFF) {
+			/* possible marker - check next byte */
+			if (fread(&data, sizeof(data), 1, reader->file) != sizeof(data))
+				return false;
+
+			if (data != 0)
+				return false;
+		}
+
+		*bit = data & 0x01;
+		reader->buffer = data >> 1;
+		reader->bit_pos = 7;
+		return true;
+	}
+
+	*bit = reader->buffer & 0x01;
+	reader->buffer >>= 1;
+	reader->bit_pos--;
+	return true;
+}
+
+bool bit_reader_next_bits(struct bit_reader *reader, uint16_t *bits, uint8_t num)
+{
+	assert(reader != NULL);
+	assert(bits   != NULL);
+	assert(num <= 16);
+
+	uint8_t tmp = 0;
+
+	for (int i = 0; i < num; i++) {
+		uint8_t bit;
+		if (!bit_reader_next_bit(reader, &bit))
+			return false;
+
+		tmp = (tmp << 1) | (bit & 0x01);
+	}
+
+	*bits = tmp;
+	return true;
+}
+

bit_reader.h

@@ -0,0 +1,18 @@
+/*
+ * @file bit_reader.h
+ * @author Fabjan Sukalia <[email protected]>
+ * @date 2016-02-03
+ * @brief Module to read bitwise from a file.
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+struct bit_reader;
+
+struct bit_reader *bit_reader_create(FILE *in);
+void bit_reader_destroy(struct bit_reader *reader);
+bool bit_reader_next_bit(struct bit_reader *reader, uint8_t *bit);
+bool bit_reader_next_bits(struct bit_reader *reader, uint16_t *bits, uint8_t num);
+