diff options
Diffstat (limited to 'dep/src/zlib/inffast.c')
| -rw-r--r-- | dep/src/zlib/inffast.c | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/dep/src/zlib/inffast.c b/dep/src/zlib/inffast.c index 25f57b424c0..bbee92ed1e6 100644 --- a/dep/src/zlib/inffast.c +++ b/dep/src/zlib/inffast.c @@ -2,11 +2,14 @@ * Copyright (C) 1995-2004 Mark Adler * For conditions of distribution and use, see copyright notice in zlib.h */ + #include "zutil.h" #include "inftrees.h" #include "inflate.h" #include "inffast.h" + #ifndef ASMINF + /* Allow machine dependent optimization for post-increment or pre-increment. Based on testing to date, Pre-increment preferred for: @@ -25,6 +28,7 @@ # define OFF 1 # define PUP(a) *++(a) #endif + /* Decode literal, length, and distance codes and write out the resulting literal and match bytes until either not enough input or output is @@ -32,22 +36,29 @@ When large enough input and output buffers are supplied to inflate(), for example, a 16K input buffer and a 64K output buffer, more than 95% of the inflate execution time is spent in this routine. + Entry assumptions: + state->mode == LEN strm->avail_in >= 6 strm->avail_out >= 258 start >= strm->avail_out state->bits < 8 + On return, state->mode is one of: + LEN -- ran out of enough output space or enough available input TYPE -- reached end of block code, inflate() to interpret next block BAD -- error in block data + Notes: + - The maximum input bits used by a length/distance pair is 15 bits for the length code, 5 bits for the length extra, 15 bits for the distance code, and 13 bits for the distance extra. This totals 48 bits, or six bytes. Therefore if strm->avail_in >= 6, then there is enough input to avoid checking for available input while decoding. + - The maximum bytes that a single length/distance pair can output is 258 bytes, which is the maximum length that can be coded. inflate_fast() requires strm->avail_out >= 258 for each loop to avoid checking for @@ -82,6 +93,7 @@ unsigned start; /* inflate()'s starting value for strm->avail_out */ unsigned len; /* match length, unused bytes */ unsigned dist; /* match distance */ unsigned char FAR *from; /* where to copy match from */ + /* copy state to local variables */ state = (struct inflate_state FAR *)strm->state; in = strm->next_in - OFF; @@ -102,6 +114,7 @@ unsigned start; /* inflate()'s starting value for strm->avail_out */ dcode = state->distcode; lmask = (1U << state->lenbits) - 1; dmask = (1U << state->distbits) - 1; + /* decode literals and length/distances until end-of-block or not enough input data or output space */ do { @@ -270,11 +283,13 @@ unsigned start; /* inflate()'s starting value for strm->avail_out */ break; } } while (in < last && out < end); + /* return unused bytes (on entry, bits < 8, so in won't go too far back) */ len = bits >> 3; in -= len; bits -= len << 3; hold &= (1U << bits) - 1; + /* update state and return */ strm->next_in = in + OFF; strm->next_out = out + OFF; @@ -285,6 +300,7 @@ unsigned start; /* inflate()'s starting value for strm->avail_out */ state->bits = bits; return; } + /* inflate_fast() speedups that turned out slower (on a PowerPC G3 750CXe): - Using bit fields for code structure @@ -298,4 +314,5 @@ unsigned start; /* inflate()'s starting value for strm->avail_out */ - Larger unrolled copy loops (three is about right) - Moving len -= 3 statement into middle of loop */ + #endif /* !ASMINF */ |