diff options
| -rw-r--r-- | Objects/fileobject.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/Objects/fileobject.c b/Objects/fileobject.c index d3b9894..b9fa0fc 100644 --- a/Objects/fileobject.c +++ b/Objects/fileobject.c @@ -422,13 +422,22 @@ new_buffersize(f, currentsize) struct stat st; if (fstat(fileno(f->f_fp), &st) == 0) { end = st.st_size; + /* The following is not a bug: we really need to call lseek() + *and* ftell(). The reason is that some stdio libraries + mistakenly flush their buffer when ftell() is called and + the lseek() call it makes fails, thereby throwing away + data that cannot be recovered in any way. To avoid this, + we first test lseek(), and only call ftell() if lseek() + works. We can't use the lseek() value either, because we + need to take the amount of buffered data into account. + (Yet another reason why stdio stinks. :-) */ pos = lseek(fileno(f->f_fp), 0L, SEEK_CUR); if (pos >= 0) pos = ftell(f->f_fp); if (pos < 0) clearerr(f->f_fp); if (end > pos && pos >= 0) - return end - pos + 1; + return currentsize + end - pos + 1; /* Add 1 so if the file were to grow we'd notice. */ } #endif @@ -482,7 +491,7 @@ file_read(f, args) if (bytesread < buffersize) break; if (bytesrequested < 0) { - buffersize = bytesread + new_buffersize(f, buffersize); + buffersize = new_buffersize(f, buffersize); if (_PyString_Resize(&v, buffersize) < 0) return NULL; } |