Zlib: Use defines for inffast
Zlib's inffast uses a handful of magic numbers. It would be easier to
read and maintain if these magic numbers were instead #defines.
NigelTao@ wrote this code to clean up the magic numbers in
https://chromium-review.googlesource.com/c/chromium/src/+/601694
Nigel gave me permission to make a separate pull request to separate out
just the magic number cleaning.
BUG=764431
Change-Id: I0a62e31e98d4f3afcc64bd096e62a4b4b175644b
Reviewed-on: https://chromium-review.googlesource.com/663424
Commit-Queue: Chris Blume <cblume@google.com>
Reviewed-by: Adenilson Cavalcanti <cavalcantii@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#502982}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 5d7c2b78db0e96c769dee8d4ed3a9aeac8ef21d5diff --git a/0003-use-defines-for-inffast.patch b/0003-use-defines-for-inffast.patch
new file mode 100644
index 0000000..9413934
--- /dev/null
+++ b/0003-use-defines-for-inffast.patch
@@ -0,0 +1,120 @@
+From 8626f3ea324e1e6f15229722761617063a70b96b Mon Sep 17 00:00:00 2001
+From: Chris Blume <cblume@google.com>
+Date: Tue, 12 Sep 2017 11:17:55 -0700
+Subject: [PATCH 1/1] Zlib: Use defines for inffast
+
+Zlib's inffast uses a handful of magic numbers. It would be easier to
+read and maintain if these magic numbers were instead #defines.
+
+NigelTao@ wrote this code to clean up the magic numbers in
+https://chromium-review.googlesource.com/c/chromium/src/+/601694
+
+Nigel gave me permission to make a separate pull request to separate out
+just the magic number cleaning.
+
+BUG=764431
+---
+ third_party/zlib/infback.c | 3 ++-
+ third_party/zlib/inffast.c | 15 +++++++++------
+ third_party/zlib/inffast.h | 15 +++++++++++++++
+ third_party/zlib/inflate.c | 3 ++-
+ 4 files changed, 28 insertions(+), 8 deletions(-)
+
+diff --git a/third_party/zlib/infback.c b/third_party/zlib/infback.c
+index 59679ecbfc5d..b93ef478e957 100644
+--- a/third_party/zlib/infback.c
++++ b/third_party/zlib/infback.c
+@@ -480,7 +480,8 @@ void FAR *out_desc;
+
+ case LEN:
+ /* use inflate_fast() if we have enough input and output */
+- if (have >= 6 && left >= 258) {
++ if (have >= INFLATE_FAST_MIN_HAVE &&
++ left >= INFLATE_FAST_MIN_LEFT) {
+ RESTORE();
+ if (state->whave < state->wsize)
+ state->whave = state->wsize - left;
+diff --git a/third_party/zlib/inffast.c b/third_party/zlib/inffast.c
+index 0dbd1dbc09f2..66c0d02494a9 100644
+--- a/third_party/zlib/inffast.c
++++ b/third_party/zlib/inffast.c
+@@ -23,8 +23,8 @@
+ Entry assumptions:
+
+ state->mode == LEN
+- strm->avail_in >= 6
+- strm->avail_out >= 258
++ strm->avail_in >= INFLATE_FAST_MIN_HAVE
++ strm->avail_out >= INFLATE_FAST_MIN_LEFT
+ start >= strm->avail_out
+ state->bits < 8
+
+@@ -80,10 +80,10 @@ unsigned start; /* inflate()'s starting value for strm->avail_out */
+ /* copy state to local variables */
+ state = (struct inflate_state FAR *)strm->state;
+ in = strm->next_in;
+- last = in + (strm->avail_in - 5);
++ last = in + (strm->avail_in - (INFLATE_FAST_MIN_HAVE - 1));
+ out = strm->next_out;
+ beg = out - (start - strm->avail_out);
+- end = out + (strm->avail_out - 257);
++ end = out + (strm->avail_out - (INFLATE_FAST_MIN_LEFT - 1));
+ #ifdef INFLATE_STRICT
+ dmax = state->dmax;
+ #endif
+@@ -298,9 +298,12 @@ unsigned start; /* inflate()'s starting value for strm->avail_out */
+ /* update state and return */
+ strm->next_in = in;
+ strm->next_out = out;
+- strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
++ strm->avail_in = (unsigned)(in < last ?
++ (INFLATE_FAST_MIN_HAVE - 1) + (last - in) :
++ (INFLATE_FAST_MIN_HAVE - 1) - (in - last));
+ strm->avail_out = (unsigned)(out < end ?
+- 257 + (end - out) : 257 - (out - end));
++ (INFLATE_FAST_MIN_LEFT - 1) + (end - out) :
++ (INFLATE_FAST_MIN_LEFT - 1) - (out - end));
+ state->hold = hold;
+ state->bits = bits;
+ return;
+diff --git a/third_party/zlib/inffast.h b/third_party/zlib/inffast.h
+index e5c1aa4ca8cd..dda6bc82cc3b 100644
+--- a/third_party/zlib/inffast.h
++++ b/third_party/zlib/inffast.h
+@@ -8,4 +8,19 @@
+ subject to change. Applications should only use zlib.h.
+ */
+
++
++/* INFLATE_FAST_MIN_LEFT is the minimum number of output bytes that are left,
++ so that we can call inflate_fast safely with only one up front bounds check.
++ One length-distance code pair can copy up to 258 bytes.
++ */
++#define INFLATE_FAST_MIN_LEFT 258
++
++/* INFLATE_FAST_MIN_HAVE is the minimum number of input bytes that we have, so
++ that we can call inflate_fast safely with only one up front bounds check.
++ One length-distance code pair (as two Huffman encoded values of up to 15
++ bits each) plus any additional bits (up to 5 for length and 13 for distance)
++ can require reading up to 48 bits, or 6 bytes.
++ */
++#define INFLATE_FAST_MIN_HAVE 6
++
+ void ZLIB_INTERNAL inflate_fast OF((z_streamp strm, unsigned start));
+diff --git a/third_party/zlib/inflate.c b/third_party/zlib/inflate.c
+index cc38b983485b..257b9a982668 100644
+--- a/third_party/zlib/inflate.c
++++ b/third_party/zlib/inflate.c
+@@ -1044,7 +1044,8 @@ int flush;
+ case LEN_:
+ state->mode = LEN;
+ case LEN:
+- if (have >= 6 && left >= 258) {
++ if (have >= INFLATE_FAST_MIN_HAVE &&
++ left >= INFLATE_FAST_MIN_LEFT) {
+ RESTORE();
+ inflate_fast(strm, out);
+ LOAD();
+--
+2.14.1.581.gf28d330327-goog
+
diff --git a/README.chromium b/README.chromium
index 8658580..989706c 100644
--- a/README.chromium
+++ b/README.chromium
@@ -28,3 +28,5 @@
https://github.com/jtkukunas/zlib/
- 0002-uninitializedcheck.patch: default-initialize state->check, see
crbug.com/697481
+ - 0003-arm-inffast.patch: ARM optimized inflate using NEON.
+ - 0003-use-defines-for-inffast.patch: replace magic numbers with defines
diff --git a/infback.c b/infback.c
index 59679ec..b93ef47 100644
--- a/infback.c
+++ b/infback.c
@@ -480,7 +480,8 @@
case LEN:
/* use inflate_fast() if we have enough input and output */
- if (have >= 6 && left >= 258) {
+ if (have >= INFLATE_FAST_MIN_HAVE &&
+ left >= INFLATE_FAST_MIN_LEFT) {
RESTORE();
if (state->whave < state->wsize)
state->whave = state->wsize - left;
diff --git a/inffast.c b/inffast.c
index 0dbd1db..66c0d02 100644
--- a/inffast.c
+++ b/inffast.c
@@ -23,8 +23,8 @@
Entry assumptions:
state->mode == LEN
- strm->avail_in >= 6
- strm->avail_out >= 258
+ strm->avail_in >= INFLATE_FAST_MIN_HAVE
+ strm->avail_out >= INFLATE_FAST_MIN_LEFT
start >= strm->avail_out
state->bits < 8
@@ -80,10 +80,10 @@
/* copy state to local variables */
state = (struct inflate_state FAR *)strm->state;
in = strm->next_in;
- last = in + (strm->avail_in - 5);
+ last = in + (strm->avail_in - (INFLATE_FAST_MIN_HAVE - 1));
out = strm->next_out;
beg = out - (start - strm->avail_out);
- end = out + (strm->avail_out - 257);
+ end = out + (strm->avail_out - (INFLATE_FAST_MIN_LEFT - 1));
#ifdef INFLATE_STRICT
dmax = state->dmax;
#endif
@@ -298,9 +298,12 @@
/* update state and return */
strm->next_in = in;
strm->next_out = out;
- strm->avail_in = (unsigned)(in < last ? 5 + (last - in) : 5 - (in - last));
+ strm->avail_in = (unsigned)(in < last ?
+ (INFLATE_FAST_MIN_HAVE - 1) + (last - in) :
+ (INFLATE_FAST_MIN_HAVE - 1) - (in - last));
strm->avail_out = (unsigned)(out < end ?
- 257 + (end - out) : 257 - (out - end));
+ (INFLATE_FAST_MIN_LEFT - 1) + (end - out) :
+ (INFLATE_FAST_MIN_LEFT - 1) - (out - end));
state->hold = hold;
state->bits = bits;
return;
diff --git a/inffast.h b/inffast.h
index e5c1aa4..ec9272a 100644
--- a/inffast.h
+++ b/inffast.h
@@ -8,4 +8,18 @@
subject to change. Applications should only use zlib.h.
*/
+/* INFLATE_FAST_MIN_LEFT is the minimum number of output bytes that are left,
+ so that we can call inflate_fast safely with only one up front bounds check.
+ One length-distance code pair can copy up to 258 bytes.
+ */
+#define INFLATE_FAST_MIN_LEFT 258
+
+/* INFLATE_FAST_MIN_HAVE is the minimum number of input bytes that we have, so
+ that we can call inflate_fast safely with only one up front bounds check.
+ One length-distance code pair (as two Huffman encoded values of up to 15
+ bits each) plus any additional bits (up to 5 for length and 13 for distance)
+ can require reading up to 48 bits, or 6 bytes.
+ */
+#define INFLATE_FAST_MIN_HAVE 6
+
void ZLIB_INTERNAL inflate_fast OF((z_streamp strm, unsigned start));
diff --git a/inflate.c b/inflate.c
index 69b769a..bec9497 100644
--- a/inflate.c
+++ b/inflate.c
@@ -1043,7 +1043,8 @@
case LEN_:
state->mode = LEN;
case LEN:
- if (have >= 6 && left >= 258) {
+ if (have >= INFLATE_FAST_MIN_HAVE &&
+ left >= INFLATE_FAST_MIN_LEFT) {
RESTORE();
inflate_fast(strm, out);
LOAD();