[zlib] Re-sync with zlib 1.2.12, patch 14 of N

Ported:
- Avoid adding empty gzip member after gzflush with Z_FINISH.
- Fix error in comment on the polynomial representation of a byte.
- Clarify gz* function interfaces, referring to parameter names.
- Change macro name in inflate.c to avoid collision in VxWorks.
- Replace black/white with allow/block. (theresa-m)
- Add fallthrough comments for gcc.

Bug: 1032721
Change-Id: Iddabef8450dca9dced3df58473a0ecb197796dc4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3611483
Reviewed-by: Noel Gordon <noel@chromium.org>
Reviewed-by: Chris Blume <cblume@chromium.org>
Commit-Queue: Adenilson Cavalcanti <cavalcantii@chromium.org>
Cr-Commit-Position: refs/heads/main@{#996983}
NOKEYCHECK=True
GitOrigin-RevId: c47a52f8f7950377f45f850cf66092a4a6033fa6
diff --git a/contrib/optimizations/inflate.c b/contrib/optimizations/inflate.c
index 4841cd9..5d69770 100644
--- a/contrib/optimizations/inflate.c
+++ b/contrib/optimizations/inflate.c
@@ -460,10 +460,10 @@
 
 /* check function to use adler32() for zlib or crc32() for gzip */
 #ifdef GUNZIP
-#  define UPDATE(check, buf, len) \
+#  define UPDATE_CHECK(check, buf, len) \
     (state->flags ? crc32(check, buf, len) : adler32(check, buf, len))
 #else
-#  define UPDATE(check, buf, len) adler32(check, buf, len)
+#  define UPDATE_CHECK(check, buf, len) adler32(check, buf, len)
 #endif
 
 /* check macros for header crc */
@@ -735,6 +735,7 @@
                 CRC2(state->check, hold);
             INITBITS();
             state->mode = TIME;
+                /* fallthrough */
         case TIME:
             NEEDBITS(32);
             if (state->head != Z_NULL)
@@ -743,6 +744,7 @@
                 CRC4(state->check, hold);
             INITBITS();
             state->mode = OS;
+                /* fallthrough */
         case OS:
             NEEDBITS(16);
             if (state->head != Z_NULL) {
@@ -753,6 +755,7 @@
                 CRC2(state->check, hold);
             INITBITS();
             state->mode = EXLEN;
+                /* fallthrough */
         case EXLEN:
             if (state->flags & 0x0400) {
                 NEEDBITS(16);
@@ -766,6 +769,7 @@
             else if (state->head != Z_NULL)
                 state->head->extra = Z_NULL;
             state->mode = EXTRA;
+                /* fallthrough */
         case EXTRA:
             if (state->flags & 0x0400) {
                 copy = state->length;
@@ -788,6 +792,7 @@
             }
             state->length = 0;
             state->mode = NAME;
+                /* fallthrough */
         case NAME:
             if (state->flags & 0x0800) {
                 if (have == 0) goto inf_leave;
@@ -809,6 +814,7 @@
                 state->head->name = Z_NULL;
             state->length = 0;
             state->mode = COMMENT;
+                /* fallthrough */
         case COMMENT:
             if (state->flags & 0x1000) {
                 if (have == 0) goto inf_leave;
@@ -829,6 +835,7 @@
             else if (state->head != Z_NULL)
                 state->head->comment = Z_NULL;
             state->mode = HCRC;
+                /* fallthrough */
         case HCRC:
             if (state->flags & 0x0200) {
                 NEEDBITS(16);
@@ -852,6 +859,7 @@
             strm->adler = state->check = ZSWAP32(hold);
             INITBITS();
             state->mode = DICT;
+                /* fallthrough */
         case DICT:
             if (state->havedict == 0) {
                 RESTORE();
@@ -859,8 +867,10 @@
             }
             strm->adler = state->check = adler32(0L, Z_NULL, 0);
             state->mode = TYPE;
+                /* fallthrough */
         case TYPE:
             if (flush == Z_BLOCK || flush == Z_TREES) goto inf_leave;
+                /* fallthrough */
         case TYPEDO:
             if (state->last) {
                 BYTEBITS();
@@ -911,8 +921,10 @@
             INITBITS();
             state->mode = COPY_;
             if (flush == Z_TREES) goto inf_leave;
+                /* fallthrough */
         case COPY_:
             state->mode = COPY;
+                /* fallthrough */
         case COPY:
             copy = state->length;
             if (copy) {
@@ -948,6 +960,7 @@
             Tracev((stderr, "inflate:       table sizes ok\n"));
             state->have = 0;
             state->mode = LENLENS;
+                /* fallthrough */
         case LENLENS:
             while (state->have < state->ncode) {
                 NEEDBITS(3);
@@ -969,6 +982,7 @@
             Tracev((stderr, "inflate:       code lengths ok\n"));
             state->have = 0;
             state->mode = CODELENS;
+                /* fallthrough */
         case CODELENS:
             while (state->have < state->nlen + state->ndist) {
                 for (;;) {
@@ -1052,8 +1066,10 @@
             Tracev((stderr, "inflate:       codes ok\n"));
             state->mode = LEN_;
             if (flush == Z_TREES) goto inf_leave;
+                /* fallthrough */
         case LEN_:
             state->mode = LEN;
+                /* fallthrough */
         case LEN:
             if (have >= INFLATE_FAST_MIN_INPUT &&
                 left >= INFLATE_FAST_MIN_OUTPUT) {
@@ -1104,6 +1120,7 @@
             }
             state->extra = (unsigned)(here.op) & 15;
             state->mode = LENEXT;
+                /* fallthrough */
         case LENEXT:
             if (state->extra) {
                 NEEDBITS(state->extra);
@@ -1114,6 +1131,7 @@
             Tracevv((stderr, "inflate:         length %u\n", state->length));
             state->was = state->length;
             state->mode = DIST;
+                /* fallthrough */
         case DIST:
             for (;;) {
                 here = state->distcode[BITS(state->distbits)];
@@ -1141,6 +1159,7 @@
             state->offset = (unsigned)here.val;
             state->extra = (unsigned)(here.op) & 15;
             state->mode = DISTEXT;
+                /* fallthrough */
         case DISTEXT:
             if (state->extra) {
                 NEEDBITS(state->extra);
@@ -1157,6 +1176,7 @@
 #endif
             Tracevv((stderr, "inflate:         distance %u\n", state->offset));
             state->mode = MATCH;
+                /* fallthrough */
         case MATCH:
             if (left == 0) goto inf_leave;
             copy = out - left;
@@ -1215,7 +1235,7 @@
                 state->total += out;
                 if ((state->wrap & 4) && out)
                     strm->adler = state->check =
-                        UPDATE(state->check, put - out, out);
+                        UPDATE_CHECK(state->check, put - out, out);
                 out = left;
                 if ((state->wrap & 4) && (
 #ifdef GUNZIP
@@ -1231,6 +1251,7 @@
             }
 #ifdef GUNZIP
             state->mode = LENGTH;
+                /* fallthrough */
         case LENGTH:
             if (state->wrap && state->flags) {
                 NEEDBITS(32);
@@ -1244,6 +1265,7 @@
             }
 #endif
             state->mode = DONE;
+                /* fallthrough */
         case DONE:
             ret = Z_STREAM_END;
             goto inf_leave;
@@ -1253,6 +1275,7 @@
         case MEM:
             return Z_MEM_ERROR;
         case SYNC:
+                /* fallthrough */
         default:
             return Z_STREAM_ERROR;
         }
@@ -1288,7 +1311,7 @@
     state->total += out;
     if ((state->wrap & 4) && out)
         strm->adler = state->check =
-            UPDATE(state->check, strm->next_out - out, out);
+            UPDATE_CHECK(state->check, strm->next_out - out, out);
     strm->data_type = (int)state->bits + (state->last ? 64 : 0) +
                       (state->mode == TYPE ? 128 : 0) +
                       (state->mode == LEN_ || state->mode == COPY_ ? 256 : 0);
diff --git a/crc32.c b/crc32.c
index 41fe891..b83d6e4 100644
--- a/crc32.c
+++ b/crc32.c
@@ -230,7 +230,7 @@
   is just exclusive-or, and multiplying a polynomial by x is a right shift by
   one. If we call the above polynomial p, and represent a byte as the
   polynomial q, also with the lowest power in the most significant bit (so the
-  byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
+  byte 0xb1 is the polynomial x^7+x^3+x^2+1), then the CRC is (q*x^32) mod p,
   where a mod b means the remainder after dividing a by b.
 
   This calculation is done using the shift-register method of multiplying and
diff --git a/gzguts.h b/gzguts.h
index 6378d46..fc712dc 100644
--- a/gzguts.h
+++ b/gzguts.h
@@ -190,6 +190,7 @@
         /* just for writing */
     int level;              /* compression level */
     int strategy;           /* compression strategy */
+    int reset;              /* true if a reset is pending after a Z_FINISH */
         /* seek request */
     z_off64_t skip;         /* amount to skip (already rewound if backwards) */
     int seek;               /* true if seek request pending */
diff --git a/gzlib.c b/gzlib.c
index 4838bf0..f6b3b40 100644
--- a/gzlib.c
+++ b/gzlib.c
@@ -81,6 +81,8 @@
         state->past = 0;            /* have not read past end yet */
         state->how = LOOK;          /* look for gzip header */
     }
+    else                            /* for writing ... */
+        state->reset = 0;           /* no deflateReset pending */
     state->seek = 0;                /* no seek request pending */
     gz_error(state, Z_OK, NULL);    /* clear error */
     state->x.pos = 0;               /* no uncompressed data yet */
diff --git a/gzwrite.c b/gzwrite.c
index 5238133..85b576b 100644
--- a/gzwrite.c
+++ b/gzwrite.c
@@ -97,6 +97,15 @@
         return 0;
     }
 
+    /* check for a pending reset */
+    if (state->reset) {
+        /* don't start a new gzip member unless there is data to write */
+        if (strm->avail_in == 0)
+            return 0;
+        deflateReset(strm);
+        state->reset = 0;
+    }
+
     /* run deflate() on provided input until it produces no more output */
     ret = Z_OK;
     do {
@@ -134,7 +143,7 @@
 
     /* if that completed a deflate stream, allow another to start */
     if (flush == Z_FINISH)
-        deflateReset(strm);
+        state->reset = 1;
 
     /* all done, no errors */
     return 0;
diff --git a/infback.c b/infback.c
index aab14b4..5f56c8c 100644
--- a/infback.c
+++ b/infback.c
@@ -477,6 +477,7 @@
             }
             Tracev((stderr, "inflate:       codes ok\n"));
             state->mode = LEN;
+                /* fallthrough */
 
         case LEN:
             /* use inflate_fast() if we have enough input and output */
diff --git a/inflate.c b/inflate.c
index 7543c33..71f336f 100644
--- a/inflate.c
+++ b/inflate.c
@@ -449,10 +449,10 @@
 
 /* check function to use adler32() for zlib or crc32() for gzip */
 #ifdef GUNZIP
-#  define UPDATE(check, buf, len) \
+#  define UPDATE_CHECK(check, buf, len) \
     (state->flags ? crc32(check, buf, len) : adler32(check, buf, len))
 #else
-#  define UPDATE(check, buf, len) adler32(check, buf, len)
+#  define UPDATE_CHECK(check, buf, len) adler32(check, buf, len)
 #endif
 
 /* check macros for header crc */
@@ -724,6 +724,7 @@
                 CRC2(state->check, hold);
             INITBITS();
             state->mode = TIME;
+                /* fallthrough */
         case TIME:
             NEEDBITS(32);
             if (state->head != Z_NULL)
@@ -732,6 +733,7 @@
                 CRC4(state->check, hold);
             INITBITS();
             state->mode = OS;
+                /* fallthrough */
         case OS:
             NEEDBITS(16);
             if (state->head != Z_NULL) {
@@ -742,6 +744,7 @@
                 CRC2(state->check, hold);
             INITBITS();
             state->mode = EXLEN;
+                /* fallthrough */
         case EXLEN:
             if (state->flags & 0x0400) {
                 NEEDBITS(16);
@@ -755,6 +758,7 @@
             else if (state->head != Z_NULL)
                 state->head->extra = Z_NULL;
             state->mode = EXTRA;
+                /* fallthrough */
         case EXTRA:
             if (state->flags & 0x0400) {
                 copy = state->length;
@@ -777,6 +781,7 @@
             }
             state->length = 0;
             state->mode = NAME;
+                /* fallthrough */
         case NAME:
             if (state->flags & 0x0800) {
                 if (have == 0) goto inf_leave;
@@ -798,6 +803,7 @@
                 state->head->name = Z_NULL;
             state->length = 0;
             state->mode = COMMENT;
+                /* fallthrough */
         case COMMENT:
             if (state->flags & 0x1000) {
                 if (have == 0) goto inf_leave;
@@ -818,6 +824,7 @@
             else if (state->head != Z_NULL)
                 state->head->comment = Z_NULL;
             state->mode = HCRC;
+                /* fallthrough */
         case HCRC:
             if (state->flags & 0x0200) {
                 NEEDBITS(16);
@@ -841,6 +848,7 @@
             strm->adler = state->check = ZSWAP32(hold);
             INITBITS();
             state->mode = DICT;
+                /* fallthrough */
         case DICT:
             if (state->havedict == 0) {
                 RESTORE();
@@ -848,8 +856,10 @@
             }
             strm->adler = state->check = adler32(0L, Z_NULL, 0);
             state->mode = TYPE;
+                /* fallthrough */
         case TYPE:
             if (flush == Z_BLOCK || flush == Z_TREES) goto inf_leave;
+                /* fallthrough */
         case TYPEDO:
             if (state->last) {
                 BYTEBITS();
@@ -900,8 +910,10 @@
             INITBITS();
             state->mode = COPY_;
             if (flush == Z_TREES) goto inf_leave;
+                /* fallthrough */
         case COPY_:
             state->mode = COPY;
+                /* fallthrough */
         case COPY:
             copy = state->length;
             if (copy) {
@@ -937,6 +949,7 @@
             Tracev((stderr, "inflate:       table sizes ok\n"));
             state->have = 0;
             state->mode = LENLENS;
+                /* fallthrough */
         case LENLENS:
             while (state->have < state->ncode) {
                 NEEDBITS(3);
@@ -958,6 +971,7 @@
             Tracev((stderr, "inflate:       code lengths ok\n"));
             state->have = 0;
             state->mode = CODELENS;
+                /* fallthrough */
         case CODELENS:
             while (state->have < state->nlen + state->ndist) {
                 for (;;) {
@@ -1041,8 +1055,10 @@
             Tracev((stderr, "inflate:       codes ok\n"));
             state->mode = LEN_;
             if (flush == Z_TREES) goto inf_leave;
+                /* fallthrough */
         case LEN_:
             state->mode = LEN;
+                /* fallthrough */
         case LEN:
             if (have >= INFLATE_FAST_MIN_INPUT &&
                 left >= INFLATE_FAST_MIN_OUTPUT) {
@@ -1093,6 +1109,7 @@
             }
             state->extra = (unsigned)(here.op) & 15;
             state->mode = LENEXT;
+                /* fallthrough */
         case LENEXT:
             if (state->extra) {
                 NEEDBITS(state->extra);
@@ -1103,6 +1120,7 @@
             Tracevv((stderr, "inflate:         length %u\n", state->length));
             state->was = state->length;
             state->mode = DIST;
+                /* fallthrough */
         case DIST:
             for (;;) {
                 here = state->distcode[BITS(state->distbits)];
@@ -1130,6 +1148,7 @@
             state->offset = (unsigned)here.val;
             state->extra = (unsigned)(here.op) & 15;
             state->mode = DISTEXT;
+                /* fallthrough */
         case DISTEXT:
             if (state->extra) {
                 NEEDBITS(state->extra);
@@ -1146,6 +1165,7 @@
 #endif
             Tracevv((stderr, "inflate:         distance %u\n", state->offset));
             state->mode = MATCH;
+                /* fallthrough */
         case MATCH:
             if (left == 0) goto inf_leave;
             copy = out - left;
@@ -1205,7 +1225,7 @@
                 state->total += out;
                 if ((state->wrap & 4) && out)
                     strm->adler = state->check =
-                        UPDATE(state->check, put - out, out);
+                        UPDATE_CHECK(state->check, put - out, out);
                 out = left;
                 if ((state->wrap & 4) && (
 #ifdef GUNZIP
@@ -1221,6 +1241,7 @@
             }
 #ifdef GUNZIP
             state->mode = LENGTH;
+                /* fallthrough */
         case LENGTH:
             if (state->wrap && state->flags) {
                 NEEDBITS(32);
@@ -1234,6 +1255,7 @@
             }
 #endif
             state->mode = DONE;
+                /* fallthrough */
         case DONE:
             ret = Z_STREAM_END;
             goto inf_leave;
@@ -1243,6 +1265,7 @@
         case MEM:
             return Z_MEM_ERROR;
         case SYNC:
+                /* fallthrough */
         default:
             return Z_STREAM_ERROR;
         }
@@ -1268,7 +1291,7 @@
     state->total += out;
     if ((state->wrap & 4) && out)
         strm->adler = state->check =
-            UPDATE(state->check, strm->next_out - out, out);
+            UPDATE_CHECK(state->check, strm->next_out - out, out);
     strm->data_type = (int)state->bits + (state->last ? 64 : 0) +
                       (state->mode == TYPE ? 128 : 0) +
                       (state->mode == LEN_ || state->mode == COPY_ ? 256 : 0);
diff --git a/trees.c b/trees.c
index decaeb7..6896067 100644
--- a/trees.c
+++ b/trees.c
@@ -1091,9 +1091,9 @@
  * Check if the data type is TEXT or BINARY, using the following algorithm:
  * - TEXT if the two conditions below are satisfied:
  *    a) There are no non-portable control characters belonging to the
- *       "black list" (0..6, 14..25, 28..31).
+ *       "block list" (0..6, 14..25, 28..31).
  *    b) There is at least one printable character belonging to the
- *       "white list" (9 {TAB}, 10 {LF}, 13 {CR}, 32..255).
+ *       "allow list" (9 {TAB}, 10 {LF}, 13 {CR}, 32..255).
  * - BINARY otherwise.
  * - The following partially-portable control characters form a
  *   "gray list" that is ignored in this detection algorithm:
@@ -1103,19 +1103,19 @@
 local int detect_data_type(s)
     deflate_state *s;
 {
-    /* black_mask is the bit mask of black-listed bytes
+    /* block_mask is the bit mask of block-listed bytes
      * set bits 0..6, 14..25, and 28..31
      * 0xf3ffc07f = binary 11110011111111111100000001111111
      */
-    unsigned long black_mask = 0xf3ffc07fUL;
+    unsigned long block_mask = 0xf3ffc07fUL;
     int n;
 
-    /* Check for non-textual ("black-listed") bytes. */
-    for (n = 0; n <= 31; n++, black_mask >>= 1)
-        if ((black_mask & 1) && (s->dyn_ltree[n].Freq != 0))
+    /* Check for non-textual ("block-listed") bytes. */
+    for (n = 0; n <= 31; n++, block_mask >>= 1)
+        if ((block_mask & 1) && (s->dyn_ltree[n].Freq != 0))
             return Z_BINARY;
 
-    /* Check for textual ("white-listed") bytes. */
+    /* Check for textual ("allow-listed") bytes. */
     if (s->dyn_ltree[9].Freq != 0 || s->dyn_ltree[10].Freq != 0
             || s->dyn_ltree[13].Freq != 0)
         return Z_TEXT;
@@ -1123,7 +1123,7 @@
         if (s->dyn_ltree[n].Freq != 0)
             return Z_TEXT;
 
-    /* There are no "black-listed" or "white-listed" bytes:
+    /* There are no "block-listed" or "allow-listed" bytes:
      * this stream either is empty or has tolerated ("gray-listed") bytes only.
      */
     return Z_BINARY;
diff --git a/zlib.h b/zlib.h
index 88961b9..77510ee 100644
--- a/zlib.h
+++ b/zlib.h
@@ -1304,14 +1304,14 @@
 /*
 ZEXTERN gzFile ZEXPORT gzopen OF((const char *path, const char *mode));
 
-     Opens a gzip (.gz) file for reading or writing.  The mode parameter is as
-   in fopen ("rb" or "wb") but can also include a compression level ("wb9") or
-   a strategy: 'f' for filtered data as in "wb6f", 'h' for Huffman-only
-   compression as in "wb1h", 'R' for run-length encoding as in "wb1R", or 'F'
-   for fixed code compression as in "wb9F".  (See the description of
-   deflateInit2 for more information about the strategy parameter.)  'T' will
-   request transparent writing or appending with no compression and not using
-   the gzip format.
+     Open the gzip (.gz) file at path for reading and decompressing, or
+   compressing and writing.  The mode parameter is as in fopen ("rb" or "wb")
+   but can also include a compression level ("wb9") or a strategy: 'f' for
+   filtered data as in "wb6f", 'h' for Huffman-only compression as in "wb1h",
+   'R' for run-length encoding as in "wb1R", or 'F' for fixed code compression
+   as in "wb9F".  (See the description of deflateInit2 for more information
+   about the strategy parameter.)  'T' will request transparent writing or
+   appending with no compression and not using the gzip format.
 
      "a" can be used instead of "w" to request that the gzip stream that will
    be written be appended to the file.  "+" will result in an error, since
@@ -1341,9 +1341,9 @@
 
 ZEXTERN gzFile ZEXPORT gzdopen OF((int fd, const char *mode));
 /*
-     gzdopen associates a gzFile with the file descriptor fd.  File descriptors
-   are obtained from calls like open, dup, creat, pipe or fileno (if the file
-   has been previously opened with fopen).  The mode parameter is as in gzopen.
+     Associate a gzFile with the file descriptor fd.  File descriptors are
+   obtained from calls like open, dup, creat, pipe or fileno (if the file has
+   been previously opened with fopen).  The mode parameter is as in gzopen.
 
      The next call of gzclose on the returned gzFile will also close the file
    descriptor fd, just like fclose(fdopen(fd, mode)) closes the file descriptor
@@ -1364,13 +1364,13 @@
 
 ZEXTERN int ZEXPORT gzbuffer OF((gzFile file, unsigned size));
 /*
-     Set the internal buffer size used by this library's functions.  The
-   default buffer size is 8192 bytes.  This function must be called after
-   gzopen() or gzdopen(), and before any other calls that read or write the
-   file.  The buffer memory allocation is always deferred to the first read or
-   write.  Three times that size in buffer space is allocated.  A larger buffer
-   size of, for example, 64K or 128K bytes will noticeably increase the speed
-   of decompression (reading).
+     Set the internal buffer size used by this library's functions for file to
+   size.  The default buffer size is 8192 bytes.  This function must be called
+   after gzopen() or gzdopen(), and before any other calls that read or write
+   the file.  The buffer memory allocation is always deferred to the first read
+   or write.  Three times that size in buffer space is allocated.  A larger
+   buffer size of, for example, 64K or 128K bytes will noticeably increase the
+   speed of decompression (reading).
 
      The new buffer size also affects the maximum length for gzprintf().
 
@@ -1380,9 +1380,9 @@
 
 ZEXTERN int ZEXPORT gzsetparams OF((gzFile file, int level, int strategy));
 /*
-     Dynamically update the compression level or strategy.  See the description
-   of deflateInit2 for the meaning of these parameters.  Previously provided
-   data is flushed before the parameter change.
+     Dynamically update the compression level and strategy for file.  See the
+   description of deflateInit2 for the meaning of these parameters. Previously
+   provided data is flushed before applying the parameter changes.
 
      gzsetparams returns Z_OK if success, Z_STREAM_ERROR if the file was not
    opened for writing, Z_ERRNO if there is an error writing the flushed data,
@@ -1391,7 +1391,7 @@
 
 ZEXTERN int ZEXPORT gzread OF((gzFile file, voidp buf, unsigned len));
 /*
-     Reads the given number of uncompressed bytes from the compressed file.  If
+     Read and decompress up to len uncompressed bytes from file into buf.  If
    the input file is not in gzip format, gzread copies the given number of
    bytes into the buffer directly from the file.
 
@@ -1422,11 +1422,11 @@
 ZEXTERN z_size_t ZEXPORT gzfread OF((voidp buf, z_size_t size, z_size_t nitems,
                                      gzFile file));
 /*
-     Read up to nitems items of size size from file to buf, otherwise operating
-   as gzread() does.  This duplicates the interface of stdio's fread(), with
-   size_t request and return types.  If the library defines size_t, then
-   z_size_t is identical to size_t.  If not, then z_size_t is an unsigned
-   integer type that can contain a pointer.
+     Read and decompress up to nitems items of size size from file into buf,
+   otherwise operating as gzread() does.  This duplicates the interface of
+   stdio's fread(), with size_t request and return types.  If the library
+   defines size_t, then z_size_t is identical to size_t.  If not, then z_size_t
+   is an unsigned integer type that can contain a pointer.
 
      gzfread() returns the number of full items read of size size, or zero if
    the end of the file was reached and a full item could not be read, or if
@@ -1445,18 +1445,16 @@
    file, reseting and retrying on end-of-file, when size is not 1.
 */
 
-ZEXTERN int ZEXPORT gzwrite OF((gzFile file,
-                                voidpc buf, unsigned len));
+ZEXTERN int ZEXPORT gzwrite OF((gzFile file, voidpc buf, unsigned len));
 /*
-     Writes the given number of uncompressed bytes into the compressed file.
-   gzwrite returns the number of uncompressed bytes written or 0 in case of
-   error.
+     Compress and write the len uncompressed bytes at buf to file. gzwrite
+   returns the number of uncompressed bytes written or 0 in case of error.
 */
 
 ZEXTERN z_size_t ZEXPORT gzfwrite OF((voidpc buf, z_size_t size,
                                       z_size_t nitems, gzFile file));
 /*
-     gzfwrite() writes nitems items of size size from buf to file, duplicating
+     Compress and write nitems items of size size from buf to file, duplicating
    the interface of stdio's fwrite(), with size_t request and return types.  If
    the library defines size_t, then z_size_t is identical to size_t.  If not,
    then z_size_t is an unsigned integer type that can contain a pointer.
@@ -1469,22 +1467,22 @@
 
 ZEXTERN int ZEXPORTVA gzprintf Z_ARG((gzFile file, const char *format, ...));
 /*
-     Converts, formats, and writes the arguments to the compressed file under
-   control of the format string, as in fprintf.  gzprintf returns the number of
+     Convert, format, compress, and write the arguments (...) to file under
+   control of the string format, as in fprintf.  gzprintf returns the number of
    uncompressed bytes actually written, or a negative zlib error code in case
    of error.  The number of uncompressed bytes written is limited to 8191, or
    one less than the buffer size given to gzbuffer().  The caller should assure
    that this limit is not exceeded.  If it is exceeded, then gzprintf() will
    return an error (0) with nothing written.  In this case, there may also be a
    buffer overflow with unpredictable consequences, which is possible only if
-   zlib was compiled with the insecure functions sprintf() or vsprintf()
+   zlib was compiled with the insecure functions sprintf() or vsprintf(),
    because the secure snprintf() or vsnprintf() functions were not available.
    This can be determined using zlibCompileFlags().
 */
 
 ZEXTERN int ZEXPORT gzputs OF((gzFile file, const char *s));
 /*
-     Writes the given null-terminated string to the compressed file, excluding
+     Compress and write the given null-terminated string s to file, excluding
    the terminating null character.
 
      gzputs returns the number of characters written, or -1 in case of error.
@@ -1492,11 +1490,12 @@
 
 ZEXTERN char * ZEXPORT gzgets OF((gzFile file, char *buf, int len));
 /*
-     Reads bytes from the compressed file until len-1 characters are read, or a
-   newline character is read and transferred to buf, or an end-of-file
-   condition is encountered.  If any characters are read or if len == 1, the
-   string is terminated with a null character.  If no characters are read due
-   to an end-of-file or len < 1, then the buffer is left untouched.
+     Read and decompress bytes from file into buf, until len-1 characters are
+   read, or until a newline character is read and transferred to buf, or an
+   end-of-file condition is encountered.  If any characters are read or if len
+   is one, the string is terminated with a null character.  If no characters
+   are read due to an end-of-file or len is less than one, then the buffer is
+   left untouched.
 
      gzgets returns buf which is a null-terminated string, or it returns NULL
    for end-of-file or in case of error.  If there was an error, the contents at
@@ -1505,13 +1504,13 @@
 
 ZEXTERN int ZEXPORT gzputc OF((gzFile file, int c));
 /*
-     Writes c, converted to an unsigned char, into the compressed file.  gzputc
+     Compress and write c, converted to an unsigned char, into file.  gzputc
    returns the value that was written, or -1 in case of error.
 */
 
 ZEXTERN int ZEXPORT gzgetc OF((gzFile file));
 /*
-     Reads one byte from the compressed file.  gzgetc returns this byte or -1
+     Read and decompress one byte from file.  gzgetc returns this byte or -1
    in case of end of file or error.  This is implemented as a macro for speed.
    As such, it does not do all of the checking the other functions do.  I.e.
    it does not check to see if file is NULL, nor whether the structure file
@@ -1520,8 +1519,8 @@
 
 ZEXTERN int ZEXPORT gzungetc OF((int c, gzFile file));
 /*
-     Push one character back onto the stream to be read as the first character
-   on the next read.  At least one character of push-back is allowed.
+     Push c back onto the stream for file to be read as the first character on
+   the next read.  At least one character of push-back is always allowed.
    gzungetc() returns the character pushed, or -1 on failure.  gzungetc() will
    fail if c is -1, and may fail if a character has been pushed but not read
    yet.  If gzungetc is used immediately after gzopen or gzdopen, at least the
@@ -1532,9 +1531,9 @@
 
 ZEXTERN int ZEXPORT gzflush OF((gzFile file, int flush));
 /*
-     Flushes all pending output into the compressed file.  The parameter flush
-   is as in the deflate() function.  The return value is the zlib error number
-   (see function gzerror below).  gzflush is only permitted when writing.
+     Flush all pending output to file.  The parameter flush is as in the
+   deflate() function.  The return value is the zlib error number (see function
+   gzerror below).  gzflush is only permitted when writing.
 
      If the flush parameter is Z_FINISH, the remaining data is written and the
    gzip stream is completed in the output.  If gzwrite() is called again, a new
@@ -1549,8 +1548,8 @@
 ZEXTERN z_off_t ZEXPORT gzseek OF((gzFile file,
                                    z_off_t offset, int whence));
 
-     Sets the starting position for the next gzread or gzwrite on the given
-   compressed file.  The offset represents a number of bytes in the
+     Set the starting position to offset relative to whence for the next gzread
+   or gzwrite on file.  The offset represents a number of bytes in the
    uncompressed data stream.  The whence parameter is defined as in lseek(2);
    the value SEEK_END is not supported.
 
@@ -1567,18 +1566,18 @@
 
 ZEXTERN int ZEXPORT    gzrewind OF((gzFile file));
 /*
-     Rewinds the given file. This function is supported only for reading.
+     Rewind file. This function is supported only for reading.
 
-     gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET)
+     gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET).
 */
 
 /*
 ZEXTERN z_off_t ZEXPORT    gztell OF((gzFile file));
 
-     Returns the starting position for the next gzread or gzwrite on the given
-   compressed file.  This position represents a number of bytes in the
-   uncompressed data stream, and is zero when starting, even if appending or
-   reading a gzip stream from the middle of a file using gzdopen().
+     Return the starting position for the next gzread or gzwrite on file.
+   This position represents a number of bytes in the uncompressed data stream,
+   and is zero when starting, even if appending or reading a gzip stream from
+   the middle of a file using gzdopen().
 
      gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR)
 */
@@ -1586,22 +1585,22 @@
 /*
 ZEXTERN z_off_t ZEXPORT gzoffset OF((gzFile file));
 
-     Returns the current offset in the file being read or written.  This offset
-   includes the count of bytes that precede the gzip stream, for example when
-   appending or when using gzdopen() for reading.  When reading, the offset
-   does not include as yet unused buffered input.  This information can be used
-   for a progress indicator.  On error, gzoffset() returns -1.
+     Return the current compressed (actual) read or write offset of file.  This
+   offset includes the count of bytes that precede the gzip stream, for example
+   when appending or when using gzdopen() for reading.  When reading, the
+   offset does not include as yet unused buffered input.  This information can
+   be used for a progress indicator.  On error, gzoffset() returns -1.
 */
 
 ZEXTERN int ZEXPORT gzeof OF((gzFile file));
 /*
-     Returns true (1) if the end-of-file indicator has been set while reading,
-   false (0) otherwise.  Note that the end-of-file indicator is set only if the
-   read tried to go past the end of the input, but came up short.  Therefore,
-   just like feof(), gzeof() may return false even if there is no more data to
-   read, in the event that the last read request was for the exact number of
-   bytes remaining in the input file.  This will happen if the input file size
-   is an exact multiple of the buffer size.
+     Return true (1) if the end-of-file indicator for file has been set while
+   reading, false (0) otherwise.  Note that the end-of-file indicator is set
+   only if the read tried to go past the end of the input, but came up short.
+   Therefore, just like feof(), gzeof() may return false even if there is no
+   more data to read, in the event that the last read request was for the exact
+   number of bytes remaining in the input file.  This will happen if the input
+   file size is an exact multiple of the buffer size.
 
      If gzeof() returns true, then the read functions will return no more data,
    unless the end-of-file indicator is reset by gzclearerr() and the input file
@@ -1610,7 +1609,7 @@
 
 ZEXTERN int ZEXPORT gzdirect OF((gzFile file));
 /*
-     Returns true (1) if file is being copied directly while reading, or false
+     Return true (1) if file is being copied directly while reading, or false
    (0) if file is a gzip stream being decompressed.
 
      If the input file is empty, gzdirect() will return true, since the input
@@ -1631,8 +1630,8 @@
 
 ZEXTERN int ZEXPORT    gzclose OF((gzFile file));
 /*
-     Flushes all pending output if necessary, closes the compressed file and
-   deallocates the (de)compression state.  Note that once file is closed, you
+     Flush all pending output for file, if necessary, close file and
+   deallocate the (de)compression state.  Note that once file is closed, you
    cannot call gzerror with file, since its structures have been deallocated.
    gzclose must not be called more than once on the same file, just as free
    must not be called more than once on the same allocation.
@@ -1656,10 +1655,10 @@
 
 ZEXTERN const char * ZEXPORT gzerror OF((gzFile file, int *errnum));
 /*
-     Returns the error message for the last error which occurred on the given
-   compressed file.  errnum is set to zlib error number.  If an error occurred
-   in the file system and not in the compression library, errnum is set to
-   Z_ERRNO and the application may consult errno to get the exact error code.
+     Return the error message for the last error which occurred on file.
+   errnum is set to zlib error number.  If an error occurred in the file system
+   and not in the compression library, errnum is set to Z_ERRNO and the
+   application may consult errno to get the exact error code.
 
      The application must not modify the returned string.  Future calls to
    this function may invalidate the previously returned string.  If file is
@@ -1672,7 +1671,7 @@
 
 ZEXTERN void ZEXPORT gzclearerr OF((gzFile file));
 /*
-     Clears the error and end-of-file flags for file.  This is analogous to the
+     Clear the error and end-of-file flags for file.  This is analogous to the
    clearerr() function in stdio.  This is useful for continuing to read a gzip
    file that is being written concurrently.
 */