Add bitstream reader functions.

2 files changed, 37 insertions, 0 deletions

diff --git a/fitz/fitz.h b/fitz/fitz.h
index 685a75f3..bea851fa 100644
--- a/fitz/fitz.h
+++ b/fitz/fitz.h
@@ -499,6 +499,8 @@ struct fz_stream_s
 	int refs;
 	int dead;
 	int pos;
+	int avail;
+	int bits;
 	unsigned char *bp, *rp, *wp, *ep;
 	void *state;
 	int (*read)(fz_stream *stm, unsigned char *buf, int len);
@@ -548,6 +550,38 @@ static inline void fz_unreadbyte(fz_stream *stm)
 		stm->rp--;
 }
 
+static inline unsigned int fz_readbits(fz_stream *stm, int n)
+{
+	unsigned int x;
+
+	if (n <= stm->avail)
+	{
+		stm->avail -= n;
+		x = (stm->bits >> stm->avail) & ((1 << n) - 1);
+	}
+	else
+	{
+		x = stm->bits & ((1 << stm->avail) - 1);
+		n -= stm->avail;
+		stm->avail = 0;
+
+		while (n > 8)
+		{
+			x = (x << 8) | fz_readbyte(stm);
+			n -= 8;
+		}
+
+		if (n > 0)
+		{
+			stm->bits = fz_readbyte(stm);
+			stm->avail = 8 - n;
+			x = (x << n) | (stm->bits >> stm->avail);
+		}
+	}
+
+	return x;
+}
+
 /*
  * Data filters.
  */
diff --git a/fitz/stm_open.c b/fitz/stm_open.c
index d59062cc..b81d9176 100644
--- a/fitz/stm_open.c
+++ b/fitz/stm_open.c
@@ -13,6 +13,9 @@ fz_newstream(void *state,
 	stm->dead = 0;
 	stm->pos = 0;
 
+	stm->bits = 0;
+	stm->avail = 0;
+
 	stm->bp = stm->buf;
 	stm->rp = stm->bp;
 	stm->wp = stm->bp;