Add bit-buffer library

https://gist.github.com/hackedbellini/366ccf1cead1ba14049f

bit-buffer.c

+/*
+  Copyright (C) 2015 Thiago Bellini <hackedbellini@gmail.com>
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 2 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "bit-buffer.h"
+
+
+/*
+ * Initialize the bit buffer.
+ */
+void
+bb_init (struct BIT_BUFFER *buffer, FILE *fp)
+{
+  buffer->pos = 0;
+  buffer->bits = 0;
+  buffer->first_read = 0;
+  buffer->fp = fp;
+}
+
+/*
+ * Flush bit buffer to file.
+ */
+void
+bb_flush (struct BIT_BUFFER *buffer)
+{
+  if (buffer->pos == 0)
+    return;
+
+  /* Fill the rest of the byte with 0s */
+  while (buffer->pos < BYTE_BIT)
+    {
+      buffer->bits &= ~(1 << (BYTE_BIT - buffer->pos - 1));
+      (buffer->pos)++;
+    }
+
+  fwrite (&(buffer->bits), sizeof (byte), 1, buffer->fp);
+  buffer->pos = 0;
+  buffer->bits = 0;
+}
+
+/*
+ * Write bits to file.
+ */
+void
+bb_write (struct BIT_BUFFER *buffer, int *bits, int size)
+{
+  int i, shift_pos;
+
+  for (i = 0; i < size; i++)
+    {
+      if (buffer->pos == BYTE_BIT)
+        bb_flush (buffer);
+
+      shift_pos = BYTE_BIT - buffer->pos - 1;
+      if (bits[i])
+        buffer->bits |= (1 << shift_pos);
+      else
+        buffer->bits &= ~(1 << shift_pos);
+
+      (buffer->pos)++;
+    }
+}
+
+/*
+ * Read bits from file.
+ *
+ * The return value must be freed after being used.
+ */
+int *
+bb_read (struct BIT_BUFFER *buffer, int size)
+{
+  int i, shift_pos;
+  int *bin;
+
+  bin = malloc (size * sizeof (int));
+  for (i = 0; i < size; i++)
+    {
+      if (!buffer->first_read || buffer->pos == BYTE_BIT)
+        {
+          /* When we reach EOF, that mens any read bit was just fillers from
+             the bb_flush function. We actually don't have any more data */
+          if (!(fread (&(buffer->bits), sizeof (byte), 1, buffer->fp)))
+            return NULL;
+          buffer->first_read = 1;
+          buffer->pos = 0;
+        }
+
+      shift_pos = BYTE_BIT - buffer->pos - 1;
+      bin[i] = (buffer->bits >> shift_pos) & 1;
+
+      (buffer->pos)++;
+    }
+
+  return bin;
+}

bit-buffer.h

+#include <limits.h>
+
+#define BYTE_BIT CHAR_BIT
+typedef char byte;
+
+typedef struct BIT_BUFFER
+{
+  FILE *fp;
+  int pos;
+  byte bits;
+  int first_read;
+} BIT_BUFFER;
+
+void bb_init (struct BIT_BUFFER *buffer, FILE *fp);
+void bb_flush (struct BIT_BUFFER *buffer);
+void bb_write (struct BIT_BUFFER *buffer, int *bits, int size);
+int *bb_read (struct BIT_BUFFER *buffer, int size);