From 83b722ae4670ad289fedc0967d72c71cc5e2bab8 Mon Sep 17 00:00:00 2001 From: "P. F. Chimento" Date: Sat, 18 Jun 2011 21:16:57 +0200 Subject: [PATCH] C stdio trickery for read/write mode As pointed out in the new version of the Glk spec, when opening a file for appending, you cannot seek in it. We must open the file for appending, to make sure it is created, then close it and reopen it for read/writing. Fixes part of #34. --- libchimara/stream.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) diff --git a/libchimara/stream.c b/libchimara/stream.c index a161a4b..b9d56cd 100644 --- a/libchimara/stream.c +++ b/libchimara/stream.c @@ -358,14 +358,17 @@ file_stream_new(frefid_t fileref, glui32 fmode, glui32 rock, gboolean unicode) modestr = g_strdup(binary? "wb" : "w"); break; case filemode_WriteAppend: - modestr = g_strdup(binary? "ab" : "a"); - break; case filemode_ReadWrite: - if( g_file_test(fileref->filename, G_FILE_TEST_EXISTS) ) { - modestr = g_strdup(binary? "r+b" : "r+"); - } else { - modestr = g_strdup(binary? "w+b" : "w+"); + { + /* We have to open the file first and then close it, in order to + both make sure it exists and be able to seek in it later */ + FILE *fp = g_fopen(fileref->filename, binary? "ab" : "a"); + if(fclose(fp) != 0) { + IO_WARNING( "Error opening file", fileref->filename, g_strerror(errno) ); + return NULL; } + modestr = g_strdup(binary? "r+b" : "r+"); + } break; default: ILLEGAL_PARAM("Invalid file mode: %u", fmode); @@ -379,6 +382,12 @@ file_stream_new(frefid_t fileref, glui32 fmode, glui32 rock, gboolean unicode) return NULL; } + /* Fast-forward to the end if we are appending */ + if(fmode == filemode_WriteAppend && fseek(fp, 0, SEEK_END) != 0) { + IO_WARNING("Error fast-forwarding file to end", fileref->filename, g_strerror(errno)); + return NULL; + } + /* If they opened a file in write mode but didn't specifically get permission to do so, complain if the file already exists */ if(fileref->orig_filemode == filemode_Read && fmode != filemode_Read) { -- 2.30.2