zlib: support extraction of inflation dictionary

3 files changed, 72 insertions, 31 deletions

diff --git a/erts/doc/src/zlib.xml b/erts/doc/src/zlib.xml
index 138414a880..1a7c2d2b6f 100644
--- a/erts/doc/src/zlib.xml
+++ b/erts/doc/src/zlib.xml
@@ -576,6 +576,17 @@ unpack(Z, Compressed, Dict) ->
     </func>
 
     <func>
+      <name name="inflateGetDictionary" arity="1"/>
+      <fsummary>Return the decompression dictionary.</fsummary>
+      <desc>
+        <p>Returns the decompression dictionary currently in use
+          by the stream. This function must be called between
+          <seealso marker="#inflateInit/1"><c>inflateInit/1,2</c></seealso>
+          and <seealso marker="#inflateEnd/1"><c>inflateEnd</c></seealso>.</p>
+      </desc>
+    </func>
+
+    <func>
       <name name="open" arity="0"/>
       <fsummary>Open a stream and return a stream reference.</fsummary>
       <desc>
diff --git a/erts/emulator/drivers/common/zlib_drv.c b/erts/emulator/drivers/common/zlib_drv.c
index 440ba956d8..acbe675c41 100644
--- a/erts/emulator/drivers/common/zlib_drv.c
+++ b/erts/emulator/drivers/common/zlib_drv.c
@@ -44,30 +44,34 @@
 #define INFLATE_INIT    8
 #define INFLATE_INIT2   9
 #define INFLATE_SETDICT 10
-#define INFLATE_SYNC    11
-#define INFLATE_RESET   12
-#define INFLATE_END     13
-#define INFLATE         14
+#define INFLATE_GETDICT 11
+#define INFLATE_SYNC    12
+#define INFLATE_RESET   13
+#define INFLATE_END     14
+#define INFLATE         15
 
-#define CRC32_0         15
-#define CRC32_1         16
-#define CRC32_2         17
+#define CRC32_0         16
+#define CRC32_1         17
+#define CRC32_2         18
 
-#define SET_BUFSZ       18
-#define GET_BUFSZ       19
-#define GET_QSIZE       20
+#define SET_BUFSZ       19
+#define GET_BUFSZ       20
+#define GET_QSIZE       21
 
-#define ADLER32_1       21
-#define ADLER32_2       22
+#define ADLER32_1       22
+#define ADLER32_2       23
 
-#define CRC32_COMBINE   23
-#define ADLER32_COMBINE 24
+#define CRC32_COMBINE   24
+#define ADLER32_COMBINE 25
 
-#define INFLATE_CHUNK   25
+#define INFLATE_CHUNK   26
 
 
 #define DEFAULT_BUFSZ   4000
 
+/* According to zlib documentation, it can never exceed this */
+#define INFL_DICT_SZ    32768
+
 /* This flag is used in the same places, where zlib return codes
  * (Z_OK, Z_STREAM_END, Z_NEED_DICT) are. So, we need to set it to
  * relatively large value to avoid possible value clashes in future.
@@ -248,6 +252,18 @@ static int zlib_output(ZLibData* d)
     return zlib_output_init(d);
 }
 
+static int zlib_inflate_get_dictionary(ZLibData* d)
+{
+    ErlDrvBinary* dbin = driver_alloc_binary(INFL_DICT_SZ);
+    uInt dlen = 0;
+    int res = inflateGetDictionary(&d->s, (unsigned char*)dbin->orig_bytes, &dlen);
+    if ((res == Z_OK) && (driver_output_binary(d->port, NULL, 0, dbin, 0, dlen) < 0)) {
+        res = Z_ERRNO;
+    }
+    driver_free_binary(dbin);
+    return res;
+}
+
 static int zlib_inflate(ZLibData* d, int flush)
 {
     int res = Z_OK;
@@ -586,6 +602,11 @@ static ErlDrvSSizeT zlib_ctl(ErlDrvData drv_data, unsigned int command, char *bu
 	res = inflateSetDictionary(&d->s, (unsigned char*)buf, len);
 	return zlib_return(res, rbuf, rlen);
 
+    case INFLATE_GETDICT:
+        if (d->state != ST_INFLATE) goto badarg;
+        res = zlib_inflate_get_dictionary(d);
+        return zlib_return(res, rbuf, rlen);
+
     case INFLATE_SYNC:
 	if (d->state != ST_INFLATE) goto badarg;
 	if (len != 0) goto badarg;
diff --git a/erts/preloaded/src/zlib.erl b/erts/preloaded/src/zlib.erl
index fa0f28c5c3..8cd3e39fd7 100644
--- a/erts/preloaded/src/zlib.erl
+++ b/erts/preloaded/src/zlib.erl
@@ -23,7 +23,8 @@
 -export([open/0,close/1,deflateInit/1,deflateInit/2,deflateInit/6,
 	 deflateSetDictionary/2,deflateReset/1,deflateParams/3,
 	 deflate/2,deflate/3,deflateEnd/1,
-	 inflateInit/1,inflateInit/2,inflateSetDictionary/2,
+	 inflateInit/1,inflateInit/2,
+	 inflateSetDictionary/2,inflateGetDictionary/1,
 	 inflateSync/1,inflateReset/1,inflate/2,inflateEnd/1,
 	 inflateChunk/1, inflateChunk/2,
 	 setBufSize/2,getBufSize/1,
@@ -98,25 +99,26 @@
 -define(INFLATE_INIT,    8).
 -define(INFLATE_INIT2,   9).
 -define(INFLATE_SETDICT, 10).
--define(INFLATE_SYNC,    11).
--define(INFLATE_RESET,   12).
--define(INFLATE_END,     13).
--define(INFLATE,         14).
--define(INFLATE_CHUNK,   25).
+-define(INFLATE_GETDICT, 11).
+-define(INFLATE_SYNC,    12).
+-define(INFLATE_RESET,   13).
+-define(INFLATE_END,     14).
+-define(INFLATE,         15).
+-define(INFLATE_CHUNK,   26).
 
--define(CRC32_0,         15).
--define(CRC32_1,         16).
--define(CRC32_2,         17).
+-define(CRC32_0,         16).
+-define(CRC32_1,         17).
+-define(CRC32_2,         18).
 
--define(SET_BUFSZ,       18).
--define(GET_BUFSZ,       19).
--define(GET_QSIZE,       20).
+-define(SET_BUFSZ,       19).
+-define(GET_BUFSZ,       20).
+-define(GET_QSIZE,       21).
 
--define(ADLER32_1,       21).
--define(ADLER32_2,       22).
+-define(ADLER32_1,       22).
+-define(ADLER32_2,       23).
 
--define(CRC32_COMBINE,   23).
--define(ADLER32_COMBINE, 24).
+-define(CRC32_COMBINE,   24).
+-define(ADLER32_COMBINE, 25).
 
 %%------------------------------------------------------------------------
 
@@ -242,6 +244,13 @@ inflateInit(Z, WindowBits) ->
 inflateSetDictionary(Z, Dictionary) -> 
     call(Z, ?INFLATE_SETDICT, Dictionary).
 
+-spec inflateGetDictionary(Z) -> Dictionary when
+      Z :: zstream(),
+      Dictionary :: iolist().
+inflateGetDictionary(Z) ->
+    _ = call(Z, ?INFLATE_GETDICT, []),
+    collect(Z).
+
 -spec inflateSync(zstream()) -> 'ok'.
 inflateSync(Z) -> 
     call(Z, ?INFLATE_SYNC, []).