From: Nick Terrell <terrelln@fb.com>
Date: Mon, 12 Oct 2020 20:51:35 +0000 (-0700)
Subject: [lib] Set ZSTD_c_stable{In,Out}Buffer in ZSTD_compress2()
X-Git-Tag: v1.4.7~38^2~7
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=809b2f2071c032a71cb91441db94e3f3825d2087;p=thirdparty%2Fzstd.git

[lib] Set ZSTD_c_stable{In,Out}Buffer in ZSTD_compress2()

Sets these parameters in ZSTD_compress2() then resets them to their
orignal values after the compression call.

An alternative design could be to add a flush mode `ZSTD_e_singlePass`
which implies `ZSTD_c_stable{In,Out}Buffer` but only for a single
compression call, by directly setting the applied parameters. I've opted
for the smaller change, but this is open for discussion.
---

diff --git a/lib/compress/zstd_compress.c b/lib/compress/zstd_compress.c
index 3041c53ee..a7ab4dea3 100644
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -4364,14 +4364,22 @@ size_t ZSTD_compress2(ZSTD_CCtx* cctx,
                       void* dst, size_t dstCapacity,
                       const void* src, size_t srcSize)
 {
+    ZSTD_bufferMode_e const originalInBufferMode = cctx->requestedParams.inBufferMode;
+    ZSTD_bufferMode_e const originalOutBufferMode = cctx->requestedParams.outBufferMode;
     DEBUGLOG(4, "ZSTD_compress2 (srcSize=%u)", (unsigned)srcSize);
     ZSTD_CCtx_reset(cctx, ZSTD_reset_session_only);
+    /* Enable stable input/output buffers. */
+    cctx->requestedParams.inBufferMode = ZSTD_bm_stable;
+    cctx->requestedParams.outBufferMode = ZSTD_bm_stable;
     {   size_t oPos = 0;
         size_t iPos = 0;
         size_t const result = ZSTD_compressStream2_simpleArgs(cctx,
                                         dst, dstCapacity, &oPos,
                                         src, srcSize, &iPos,
                                         ZSTD_e_end);
+        /* Reset to the original values. */
+        cctx->requestedParams.inBufferMode = originalInBufferMode;
+        cctx->requestedParams.outBufferMode = originalOutBufferMode;
         FORWARD_IF_ERROR(result, "ZSTD_compressStream2_simpleArgs failed");
         if (result != 0) {  /* compression not completed, due to lack of output space */
             assert(oPos == dstCapacity);