From 61d29e828f33163b1750ffe1a0ac1823044d34a9 Mon Sep 17 00:00:00 2001 From: Georgios Kokolatos Date: Thu, 16 Mar 2023 15:43:29 +0000 Subject: [PATCH v2 3/3] Improve compress_lz4 documentation. Author: Tomas Vondra --- src/bin/pg_dump/compress_lz4.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/src/bin/pg_dump/compress_lz4.c b/src/bin/pg_dump/compress_lz4.c index 0c0eb09d68..f4c0910afc 100644 --- a/src/bin/pg_dump/compress_lz4.c +++ b/src/bin/pg_dump/compress_lz4.c @@ -185,10 +185,15 @@ LZ4File_get_error(CompressFileHandle *CFH) } /* - * Prepare an already alloc'ed LZ4File struct for subsequent calls. + * Prepare an already alloc'ed LZ4File struct for subsequent calls (either + * compression or decompression). * - * It creates the necessary contexts for the operations. When compressing, - * it additionally writes the LZ4 header in the output stream. + * It creates the necessary contexts for the operations. When compressing data + * (indicated by compressing=true), it additionally writes the LZ4 header in the + * output stream. + * + * Returns 0 on success. In case of a failure returns 1, and stores the error + * code in fs->errcode. */ static int LZ4File_init(LZ4File *fs, int size, bool compressing) @@ -201,9 +206,15 @@ LZ4File_init(LZ4File *fs, int size, bool compressing) fs->compressing = compressing; fs->inited = true; + /* When compressing, write LZ4 header to the output stream. */ if (fs->compressing) { fs->buflen = LZ4F_compressBound(DEFAULT_IO_BUFFER_SIZE, &fs->prefs); + + /* + * LZ4F_compressBegin requires a buffer that is greater or equal to + * LZ4F_HEADER_SIZE_MAX. Verify that the requirement is met. + */ if (fs->buflen < LZ4F_HEADER_SIZE_MAX) fs->buflen = LZ4F_HEADER_SIZE_MAX; @@ -255,9 +266,12 @@ LZ4File_init(LZ4File *fs, int size, bool compressing) /* * Read already decompressed content from the overflow buffer into 'ptr' up to * 'size' bytes, if available. If the eol_flag is set, then stop at the first - * occurrence of the new line char prior to 'size' bytes. + * occurrence of the newline char prior to 'size' bytes. * * Any unread content in the overflow buffer is moved to the beginning. + * + * Returns the number of bytes read from the overflow buffer (and copied into + * the 'ptr' buffer), or 0 if the overflow buffer is empty. */ static int LZ4File_read_overflow(LZ4File *fs, void *ptr, int size, bool eol_flag) @@ -297,6 +311,9 @@ LZ4File_read_overflow(LZ4File *fs, void *ptr, int size, bool eol_flag) * at an overflow buffer within LZ4File. Of course, when the function is * called, it will first try to consume any decompressed content already * present in the overflow buffer, before decompressing new content. + * + * Returns the number of bytes of decompressed data copied into the ptr + * buffer, or -1 in case of error. */ static int LZ4File_read_internal(LZ4File *fs, void *ptr, int ptrsize, bool eol_flag) -- 2.34.1