From 38218bc5a9a2c0ac25840a9ca52e8e6d7d0123ac Mon Sep 17 00:00:00 2001 From: "P. F. Chimento" Date: Sat, 18 Jun 2011 21:59:33 +0200 Subject: [PATCH] Fix obscure C stdio bug You cannot switch between reading and writing a file stream without a call to fseek() in between. This borrows Andrew Plotkin's solution of keeping track of what the last operation was and switching if necessary. Fixes #34, together with [743391de]. --- libchimara/stream.h | 1 + libchimara/strio.c | 77 ++++++++++++++++++++++++++++++++------------- 2 files changed, 57 insertions(+), 21 deletions(-) diff --git a/libchimara/stream.h b/libchimara/stream.h index b60e022..325b668 100644 --- a/libchimara/stream.h +++ b/libchimara/stream.h @@ -48,6 +48,7 @@ struct glk_stream_struct FILE *file_pointer; gboolean binary; gchar *filename; /* Displayable filename in UTF-8 for error handling */ + glui32 lastop; /* 0, filemode_Write, or filemode_Read */ gchar *style; /* Name of the current style */ gchar *glk_style; /* Name of the current glk style override */ diff --git a/libchimara/strio.c b/libchimara/strio.c index 24899c5..039e189 100644 --- a/libchimara/strio.c +++ b/libchimara/strio.c @@ -7,6 +7,23 @@ #include #include +/* Internal function: ensure that an fseek() is called on a file pointer in + between reading and writing operations, and vice versa. This will only come up + for ReadWrite or WriteAppend files. */ +static void +ensure_file_operation(strid_t str, glui32 op) +{ + if(str->lastop != 0 && str->lastop != op) + { + long pos = ftell(str->file_pointer); + if(pos == -1) + WARNING_S("ftell() failed", g_strerror(errno)); + if(fseek(str->file_pointer, pos, SEEK_SET) != 0) + WARNING_S("fseek() failed", g_strerror(errno)); + } + str->lastop = op; /* Not 0, because we are about to do the operation anyway */ +} + /* * **************** WRITING FUNCTIONS ******************************************** @@ -302,11 +319,13 @@ write_buffer_to_stream(strid_t str, gchar *buf, glui32 len) if(str->unicode) { gchar *writebuffer = convert_latin1_to_ucs4be_string(buf, len); + ensure_file_operation(str, filemode_Write); fwrite(writebuffer, sizeof(gchar), len * 4, str->file_pointer); g_free(writebuffer); } else /* Regular file */ { + ensure_file_operation(str, filemode_Write); fwrite(buf, sizeof(gchar), len, str->file_pointer); } } @@ -315,6 +334,7 @@ write_buffer_to_stream(strid_t str, gchar *buf, glui32 len) gchar *utf8 = convert_latin1_to_utf8(buf, len); if(utf8 != NULL) { + ensure_file_operation(str, filemode_Write); g_fprintf(str->file_pointer, "%s", utf8); g_free(utf8); } @@ -391,12 +411,14 @@ write_buffer_to_stream_uni(strid_t str, glui32 *buf, glui32 len) if(str->unicode) { gchar *writebuffer = convert_ucs4_to_ucs4be_string(buf, len); + ensure_file_operation(str, filemode_Write); fwrite(writebuffer, sizeof(gchar), len * 4, str->file_pointer); g_free(writebuffer); } else /* Regular file */ { gchar *latin1 = convert_ucs4_to_latin1_binary(buf, len); + ensure_file_operation(str, filemode_Write); fwrite(latin1, sizeof(gchar), len, str->file_pointer); g_free(latin1); } @@ -406,6 +428,7 @@ write_buffer_to_stream_uni(strid_t str, glui32 *buf, glui32 len) gchar *utf8 = convert_ucs4_to_utf8(buf, len); if(utf8 != NULL) { + ensure_file_operation(str, filemode_Write); g_fprintf(str->file_pointer, "%s", utf8); g_free(utf8); } @@ -554,10 +577,11 @@ glk_put_buffer_stream_uni(strid_t str, glui32 *buf, glui32 len) /* Internal function: Read one big-endian four-byte character from file fp and return it as a Unicode code point, or -1 on EOF */ static glsi32 -read_ucs4be_char_from_file(FILE *fp) +read_ucs4be_char_from_file(strid_t str) { unsigned char readbuffer[4]; - if(fread(readbuffer, sizeof(unsigned char), 4, fp) < 4) + ensure_file_operation(str, filemode_Read); + if(fread(readbuffer, sizeof(unsigned char), 4, str->file_pointer) < 4) return -1; /* EOF */ return readbuffer[0] << 24 | @@ -569,14 +593,15 @@ read_ucs4be_char_from_file(FILE *fp) /* Internal function: Read one UTF-8 character, which may be more than one byte, from file fp and return it as a Unicode code point, or -1 on EOF */ static glsi32 -read_utf8_char_from_file(FILE *fp) +read_utf8_char_from_file(strid_t str) { gchar readbuffer[4] = {0, 0, 0, 0}; /* Max UTF-8 width */ int foo; gunichar charresult = (gunichar)-2; + ensure_file_operation(str, filemode_Read); for(foo = 0; foo < 4 && charresult == (gunichar)-2; foo++) { - int ch = fgetc(fp); + int ch = fgetc(str->file_pointer); if(ch == EOF) return -1; readbuffer[foo] = (gchar)ch; @@ -595,16 +620,18 @@ file pointer and eight-bit flag are included in case the newline is a CR (U+000D). If the next character is LF (U+000A) then it also belongs to the newline. */ static gboolean -is_unicode_newline(glsi32 ch, FILE *fp, gboolean utf8) +is_unicode_newline(glsi32 ch, strid_t str, gboolean utf8) { if(ch == 0x0A || ch == 0x85 || ch == 0x0C || ch == 0x2028 || ch == 0x2029) return TRUE; if(ch == 0x0D) { - glsi32 ch2 = utf8? read_utf8_char_from_file(fp) : - read_ucs4be_char_from_file(fp); - if(ch2 != 0x0A) - if(fseek(fp, utf8? -1 : -4, SEEK_CUR) == -1); + glsi32 ch2 = utf8? read_utf8_char_from_file(str) : + read_ucs4be_char_from_file(str); + if(ch2 != 0x0A) { + if(fseek(str->file_pointer, utf8? -1 : -4, SEEK_CUR) == -1); WARNING_S("Seek failed on stream", g_strerror(errno) ); + str->lastop = 0; /* can read or write after a seek */ + } return TRUE; } return FALSE; @@ -642,7 +669,7 @@ get_char_stream_common(strid_t str) { if(str->unicode) { - glsi32 ch = read_ucs4be_char_from_file(str->file_pointer); + glsi32 ch = read_ucs4be_char_from_file(str); if(ch == -1) return -1; str->read_count++; @@ -650,6 +677,7 @@ get_char_stream_common(strid_t str) } else /* Regular file */ { + ensure_file_operation(str, filemode_Read); int ch = fgetc(str->file_pointer); if(ch == EOF) return -1; @@ -660,7 +688,7 @@ get_char_stream_common(strid_t str) } else /* Text mode is the same for Unicode and regular files */ { - glsi32 ch = read_utf8_char_from_file(str->file_pointer); + glsi32 ch = read_utf8_char_from_file(str); if(ch == -1) return -1; @@ -778,6 +806,7 @@ glk_get_buffer_stream(strid_t str, char *buf, glui32 len) { /* Read len characters of 4 bytes each */ unsigned char *readbuffer = g_new0(unsigned char, 4 * len); + ensure_file_operation(str, filemode_Read); size_t count = fread(readbuffer, sizeof(unsigned char), 4 * len, str->file_pointer); /* If there was an incomplete character */ if(count % 4 != 0) @@ -801,6 +830,7 @@ glk_get_buffer_stream(strid_t str, char *buf, glui32 len) } else /* Regular binary file */ { + ensure_file_operation(str, filemode_Read); size_t count = fread(buf, sizeof(char), len, str->file_pointer); str->read_count += count; return count; @@ -812,7 +842,7 @@ glk_get_buffer_stream(strid_t str, char *buf, glui32 len) int foo; for(foo = 0; foo < len; foo++) { - glsi32 ch = read_utf8_char_from_file(str->file_pointer); + glsi32 ch = read_utf8_char_from_file(str); if(ch == -1) break; str->read_count++; @@ -875,6 +905,7 @@ glk_get_buffer_stream_uni(strid_t str, glui32 *buf, glui32 len) { /* Read len characters of 4 bytes each */ unsigned char *readbuffer = g_new0(unsigned char, 4 * len); + ensure_file_operation(str, filemode_Read); size_t count = fread(readbuffer, sizeof(unsigned char), 4 * len, str->file_pointer); /* If there was an incomplete character */ if(count % 4 != 0) @@ -896,6 +927,7 @@ glk_get_buffer_stream_uni(strid_t str, glui32 *buf, glui32 len) else /* Regular binary file */ { unsigned char *readbuffer = g_new0(unsigned char, len); + ensure_file_operation(str, filemode_Read); size_t count = fread(readbuffer, sizeof(unsigned char), len, str->file_pointer); int foo; for(foo = 0; foo < count; foo++) @@ -911,7 +943,7 @@ glk_get_buffer_stream_uni(strid_t str, glui32 *buf, glui32 len) int foo; for(foo = 0; foo < len; foo++) { - glsi32 ch = read_utf8_char_from_file(str->file_pointer); + glsi32 ch = read_utf8_char_from_file(str); if(ch == -1) break; str->read_count++; @@ -1002,14 +1034,14 @@ glk_get_line_stream(strid_t str, char *buf, glui32 len) int copycount; for(copycount = 0; copycount < len - 1; copycount++) { - glsi32 ch = read_ucs4be_char_from_file(str->file_pointer); + glsi32 ch = read_ucs4be_char_from_file(str); if(ch == -1) { buf[copycount] = '\0'; return copycount; } str->read_count++; - if(is_unicode_newline(ch, str->file_pointer, FALSE)) + if(is_unicode_newline(ch, str, FALSE)) { buf[copycount++] = '\n'; buf[copycount] = '\0'; @@ -1022,6 +1054,7 @@ glk_get_line_stream(strid_t str, char *buf, glui32 len) } else /* Regular binary file */ { + ensure_file_operation(str, filemode_Read); if( !fgets(buf, len, str->file_pointer) ) { *buf = 0; return 0; @@ -1038,14 +1071,14 @@ glk_get_line_stream(strid_t str, char *buf, glui32 len) int foo; for(foo = 0; foo < len - 1; foo++) { - glsi32 ch = read_utf8_char_from_file(str->file_pointer); + glsi32 ch = read_utf8_char_from_file(str); if(ch == -1) { buf[foo] = '\0'; return foo - 1; } str->read_count++; - if(is_unicode_newline(ch, str->file_pointer, TRUE)) + if(is_unicode_newline(ch, str, TRUE)) { buf[foo] = '\n'; buf[foo + 1] = '\0'; @@ -1144,14 +1177,14 @@ glk_get_line_stream_uni(strid_t str, glui32 *buf, glui32 len) int copycount; for(copycount = 0; copycount < len - 1; copycount++) { - glsi32 ch = read_ucs4be_char_from_file(str->file_pointer); + glsi32 ch = read_ucs4be_char_from_file(str); if(ch == -1) { buf[copycount] = 0; return copycount; } str->read_count++; - if(is_unicode_newline(ch, str->file_pointer, FALSE)) + if(is_unicode_newline(ch, str, FALSE)) { buf[copycount++] = ch; /* Preserve newline types??? */ buf[copycount] = 0; @@ -1165,6 +1198,7 @@ glk_get_line_stream_uni(strid_t str, glui32 *buf, glui32 len) else /* Regular binary file */ { gchar *readbuffer = g_new0(gchar, len); + ensure_file_operation(str, filemode_Read); if( !fgets(readbuffer, len, str->file_pointer) ) { *buf = 0; return 0; @@ -1184,14 +1218,14 @@ glk_get_line_stream_uni(strid_t str, glui32 *buf, glui32 len) int foo; for(foo = 0; foo < len - 1; foo++) { - glsi32 ch = read_utf8_char_from_file(str->file_pointer); + glsi32 ch = read_utf8_char_from_file(str); if(ch == -1) { buf[foo] = 0; return foo - 1; } str->read_count++; - if(is_unicode_newline(ch, str->file_pointer, TRUE)) + if(is_unicode_newline(ch, str, TRUE)) { buf[foo] = ch; /* Preserve newline types??? */ buf[foo + 1] = 0; @@ -1329,6 +1363,7 @@ glk_stream_set_position(strid_t str, glsi32 pos, glui32 seekmode) } if(fseek(str->file_pointer, pos, whence) == -1) WARNING("Seek failed on file stream"); + str->lastop = 0; /* Either reading or writing is legal after fseek() */ break; } case STREAM_TYPE_WINDOW: -- 2.30.2