spelling/grammar/consistency review part II

[ffmpeg] / libavutil / lzo.c

diff --git a/libavutil/lzo.c b/libavutil/lzo.c
index d3849a743dc4c2280345370f7633f9505403b16a..c5557741949dbd088faba900e377dcafc08244c4 100644 (file)
--- a/libavutil/lzo.c
+++ b/libavutil/lzo.c
@@ -19,23 +19,23 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 #include "common.h"
-//! avoid e.g. MPlayers fast_memcpy, it slows things down here
+//! Avoid e.g. MPlayers fast_memcpy, it slows things down here.
 #undef memcpy
 #include <string.h>
 #include "lzo.h"
 
-//! define if we may write up to 12 bytes beyond the output buffer
+//! Define if we may write up to 12 bytes beyond the output buffer.
 #define OUTBUF_PADDED 1
-//! define if we may read up to 8 bytes beyond the input buffer
+//! Define if we may read up to 8 bytes beyond the input buffer.
 #define INBUF_PADDED 1
 typedef struct LZOContext {
-    uint8_t *in, *in_end;
+    const uint8_t *in, *in_end;
     uint8_t *out_start, *out, *out_end;
     int error;
 } LZOContext;
 
 /**
- * \brief read one byte from input buffer, avoiding overrun
+ * \brief Reads one byte from the input buffer, avoiding an overrun.
  * \return byte read
  */
 static inline int get_byte(LZOContext *c) {
@@ -52,7 +52,7 @@ static inline int get_byte(LZOContext *c) {
 #endif
 
 /**
- * \brief decode a length value in the coding used by lzo
+ * \brief Decodes a length value in the coding used by lzo.
  * \param x previous byte value
  * \param mask bits used from x
  * \return decoded length value
@@ -80,11 +80,11 @@ static inline int get_len(LZOContext *c, int x, int mask) {
 #endif
 
 /**
- * \brief copy bytes from input to output buffer with checking
+ * \brief Copies bytes from input to output buffer with checking.
  * \param cnt number of bytes to copy, must be >= 0
  */
 static inline void copy(LZOContext *c, int cnt) {
-    register uint8_t *src = c->in;
+    register const uint8_t *src = c->in;
     register uint8_t *dst = c->out;
     if (cnt > c->in_end - src) {
         cnt = FFMAX(c->in_end - src, 0);
@@ -106,8 +106,10 @@ static inline void copy(LZOContext *c, int cnt) {
     c->out = dst + cnt;
 }
 
+static inline void memcpy_backptr(uint8_t *dst, int back, int cnt);
+
 /**
- * \brief copy previously decoded bytes to current position
+ * \brief Copies previously decoded bytes to current position.
  * \param back how many bytes back we start
  * \param cnt number of bytes to copy, must be >= 0
  *
@@ -115,7 +117,7 @@ static inline void copy(LZOContext *c, int cnt) {
  * thus creating a repeating pattern with a period length of back.
  */
 static inline void copy_backptr(LZOContext *c, int back, int cnt) {
-    register uint8_t *src = &c->out[-back];
+    register const uint8_t *src = &c->out[-back];
     register uint8_t *dst = c->out;
     if (src < c->out_start || src > dst) {
         c->error |= LZO_INVALID_BACKPTR;
@@ -125,9 +127,14 @@ static inline void copy_backptr(LZOContext *c, int back, int cnt) {
         cnt = FFMAX(c->out_end - dst, 0);
         c->error |= LZO_OUTPUT_FULL;
     }
+    memcpy_backptr(dst, back, cnt);
+    c->out = dst + cnt;
+}
+
+static inline void memcpy_backptr(uint8_t *dst, int back, int cnt) {
+    const uint8_t *src = &dst[-back];
     if (back == 1) {
         memset(dst, *src, cnt);
-        dst += cnt;
     } else {
 #ifdef OUTBUF_PADDED
         COPY2(dst, src);
@@ -155,28 +162,39 @@ static inline void copy_backptr(LZOContext *c, int back, int cnt) {
             }
             memcpy(dst, src, cnt);
         }
-        dst += cnt;
     }
-    c->out = dst;
 }
 
 /**
- * \brief decode LZO 1x compressed data
+ * \brief deliberately overlapping memcpy implementation
+ * \param dst destination buffer; must be padded with 12 additional bytes
+ * \param back how many bytes back we start (the initial size of the overlapping window)
+ * \param cnt number of bytes to copy, must be >= 0
+ *
+ * cnt > back is valid, this will copy the bytes we just copied,
+ * thus creating a repeating pattern with a period length of back.
+ */
+void av_memcpy_backptr(uint8_t *dst, int back, int cnt) {
+    memcpy_backptr(dst, back, cnt);
+}
+
+/**
+ * \brief Decodes LZO 1x compressed data.
  * \param out output buffer
  * \param outlen size of output buffer, number of bytes left are returned here
  * \param in input buffer
  * \param inlen size of input buffer, number of bytes left are returned here
  * \return 0 on success, otherwise error flags, see lzo.h
  *
- * make sure all buffers are appropriately padded, in must provide
- * LZO_INPUT_PADDING, out must provide LZO_OUTPUT_PADDING additional bytes
+ * Make sure all buffers are appropriately padded, in must provide
+ * LZO_INPUT_PADDING, out must provide LZO_OUTPUT_PADDING additional bytes.
  */
-int lzo1x_decode(void *out, int *outlen, void *in, int *inlen) {
+int lzo1x_decode(void *out, int *outlen, const void *in, int *inlen) {
     int state= 0;
     int x;
     LZOContext c;
     c.in = in;
-    c.in_end = (uint8_t *)in + *inlen;
+    c.in_end = (const uint8_t *)in + *inlen;
     c.out = c.out_start = out;
     c.out_end = (uint8_t *)out + * outlen;
     c.error = 0;
@@ -267,7 +285,7 @@ STOP_TIMER("lzod")
     if (memcmp(orig, decomp, s))
         av_log(NULL, AV_LOG_ERROR, "decompression incorrect\n");
     else
-        av_log(NULL, AV_LOG_ERROR, "decompression ok\n");
+        av_log(NULL, AV_LOG_ERROR, "decompression OK\n");
     return 0;
 }
 #endif