Simplify fseek/ftell.
Another step towards _FILE_OFFSET_BITS=64 support.
Bug: http://b/24807045
Change-Id: I00b83c81a7b108176c4d9437bc32611f73b7e967
diff --git a/libc/stdio/stdio.cpp b/libc/stdio/stdio.cpp
index 1ea3ef5..1066d7f 100644
--- a/libc/stdio/stdio.cpp
+++ b/libc/stdio/stdio.cpp
@@ -35,6 +35,7 @@
#include <errno.h>
#include <fcntl.h>
+#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <sys/param.h>
@@ -51,7 +52,7 @@
#define std(flags, file) \
{0,0,0,flags,file,{0,0},0,__sF+file,__sclose,__sread,__sseek,__swrite, \
- {(unsigned char *)(__sFext+file), 0},NULL,0,{0},{0},{0,0},0,0}
+ {(unsigned char *)(__sFext+file), 0},NULL,0,{0},{0},{0,0},0}
_THREAD_PRIVATE_MUTEX(__sfp_mutex);
@@ -85,25 +86,38 @@
struct glue __sglue = { NULL, 3, __sF };
static struct glue* lastglue = &__sglue;
+class ScopedFileLock {
+ public:
+ ScopedFileLock(FILE* fp) : fp_(fp) {
+ FLOCKFILE(fp_);
+ }
+ ~ScopedFileLock() {
+ FUNLOCKFILE(fp_);
+ }
+
+ private:
+ FILE* fp_;
+};
+
static glue* moreglue(int n) {
- static FILE empty;
+ static FILE empty;
- char* data = new char[sizeof(glue) + ALIGNBYTES + n * sizeof(FILE) + n * sizeof(__sfileext)];
- if (data == nullptr) return nullptr;
+ char* data = new char[sizeof(glue) + ALIGNBYTES + n * sizeof(FILE) + n * sizeof(__sfileext)];
+ if (data == nullptr) return nullptr;
- glue* g = reinterpret_cast<glue*>(data);
- FILE* p = reinterpret_cast<FILE*>(ALIGN(data + sizeof(*g)));
- __sfileext* pext = reinterpret_cast<__sfileext*>(ALIGN(data + sizeof(*g)) + n * sizeof(FILE));
- g->next = NULL;
- g->niobs = n;
- g->iobs = p;
- while (--n >= 0) {
- *p = empty;
- _FILEEXT_SETUP(p, pext);
- p++;
- pext++;
- }
- return g;
+ glue* g = reinterpret_cast<glue*>(data);
+ FILE* p = reinterpret_cast<FILE*>(ALIGN(data + sizeof(*g)));
+ __sfileext* pext = reinterpret_cast<__sfileext*>(ALIGN(data + sizeof(*g)) + n * sizeof(FILE));
+ g->next = NULL;
+ g->niobs = n;
+ g->iobs = p;
+ while (--n >= 0) {
+ *p = empty;
+ _FILEEXT_SETUP(p, pext);
+ p++;
+ pext++;
+ }
+ return g;
}
/*
@@ -147,81 +161,155 @@
}
extern "C" __LIBC_HIDDEN__ void __libc_stdio_cleanup(void) {
- /* (void) _fwalk(fclose); */
- (void) _fwalk(__sflush); /* `cheating' */
+ // Equivalent to fflush(nullptr), but without all the locking since we're shutting down anyway.
+ _fwalk(__sflush);
}
int fclose(FILE* fp) {
- if (fp->_flags == 0) {
- // Already freed!
- errno = EBADF;
- return EOF;
- }
+ if (fp->_flags == 0) {
+ // Already freed!
+ errno = EBADF;
+ return EOF;
+ }
- FLOCKFILE(fp);
- WCIO_FREE(fp);
- int r = fp->_flags & __SWR ? __sflush(fp) : 0;
- if (fp->_close != NULL && (*fp->_close)(fp->_cookie) < 0) {
- r = EOF;
- }
- if (fp->_flags & __SMBF) free(fp->_bf._base);
- if (HASUB(fp)) FREEUB(fp);
- if (HASLB(fp)) FREELB(fp);
+ ScopedFileLock sfl(fp);
+ WCIO_FREE(fp);
+ int r = fp->_flags & __SWR ? __sflush(fp) : 0;
+ if (fp->_close != NULL && (*fp->_close)(fp->_cookie) < 0) {
+ r = EOF;
+ }
+ if (fp->_flags & __SMBF) free(fp->_bf._base);
+ if (HASUB(fp)) FREEUB(fp);
+ if (HASLB(fp)) FREELB(fp);
- // Poison this FILE so accesses after fclose will be obvious.
- fp->_file = -1;
- fp->_r = fp->_w = 0;
+ // Poison this FILE so accesses after fclose will be obvious.
+ fp->_file = -1;
+ fp->_r = fp->_w = 0;
- // Release this FILE for reuse.
- fp->_flags = 0;
- FUNLOCKFILE(fp);
- return (r);
+ // Release this FILE for reuse.
+ fp->_flags = 0;
+ return r;
}
int fileno(FILE* fp) {
- FLOCKFILE(fp);
- int result = fileno_unlocked(fp);
- FUNLOCKFILE(fp);
- return result;
+ ScopedFileLock sfl(fp);
+ return fileno_unlocked(fp);
}
-// Small standard I/O/seek/close functions.
-// These maintain the `known seek offset' for seek optimisation.
int __sread(void* cookie, char* buf, int n) {
- FILE* fp = reinterpret_cast<FILE*>(cookie);
- int ret = TEMP_FAILURE_RETRY(read(fp->_file, buf, n));
- // If the read succeeded, update the current offset.
- if (ret >= 0) {
- fp->_offset += ret;
- } else {
- fp->_flags &= ~__SOFF; // Paranoia.
- }
- return ret;
+ FILE* fp = reinterpret_cast<FILE*>(cookie);
+ return TEMP_FAILURE_RETRY(read(fp->_file, buf, n));
}
int __swrite(void* cookie, const char* buf, int n) {
- FILE* fp = reinterpret_cast<FILE*>(cookie);
- if (fp->_flags & __SAPP) {
- (void) TEMP_FAILURE_RETRY(lseek(fp->_file, 0, SEEK_END));
- }
- fp->_flags &= ~__SOFF; // In case FAPPEND mode is set.
- return TEMP_FAILURE_RETRY(write(fp->_file, buf, n));
+ FILE* fp = reinterpret_cast<FILE*>(cookie);
+ if (fp->_flags & __SAPP) {
+ // The FILE* is in append mode, but the underlying fd doesn't have O_APPEND set.
+ // We need to seek manually.
+ // TODO: can we use fcntl(2) to set O_APPEND in fdopen(3) instead?
+ TEMP_FAILURE_RETRY(lseek64(fp->_file, 0, SEEK_END));
+ }
+ return TEMP_FAILURE_RETRY(write(fp->_file, buf, n));
}
// TODO: _FILE_OFFSET_BITS=64.
fpos_t __sseek(void* cookie, fpos_t offset, int whence) {
- FILE* fp = reinterpret_cast<FILE*>(cookie);
- off_t ret = TEMP_FAILURE_RETRY(lseek(fp->_file, offset, whence));
- if (ret == -1) {
- fp->_flags &= ~__SOFF;
- } else {
- fp->_flags |= __SOFF;
- fp->_offset = ret;
- }
- return ret;
+ FILE* fp = reinterpret_cast<FILE*>(cookie);
+ return TEMP_FAILURE_RETRY(lseek(fp->_file, offset, whence));
}
int __sclose(void* cookie) {
- FILE* fp = reinterpret_cast<FILE*>(cookie);
- return close(fp->_file);
+ FILE* fp = reinterpret_cast<FILE*>(cookie);
+ return close(fp->_file);
+}
+
+static bool __file_is_seekable(FILE* fp) {
+ if (fp->_seek == nullptr) {
+ errno = ESPIPE; // Historic practice.
+ return false;
+ }
+ return true;
+}
+
+// TODO: _FILE_OFFSET_BITS=64.
+static off_t __ftello_unlocked(FILE* fp) {
+ if (!__file_is_seekable(fp)) return -1;
+
+ // Find offset of underlying I/O object, then
+ // adjust for buffered bytes.
+ __sflush(fp); // May adjust seek offset on append stream.
+ fpos_t result = (*fp->_seek)(fp->_cookie, 0, SEEK_CUR);
+ if (result == -1) {
+ return -1;
+ }
+
+ if (fp->_flags & __SRD) {
+ // Reading. Any unread characters (including
+ // those from ungetc) cause the position to be
+ // smaller than that in the underlying object.
+ result -= fp->_r;
+ if (HASUB(fp)) result -= fp->_ur;
+ } else if (fp->_flags & __SWR && fp->_p != NULL) {
+ // Writing. Any buffered characters cause the
+ // position to be greater than that in the
+ // underlying object.
+ result += fp->_p - fp->_bf._base;
+ }
+ return result;
+}
+
+int fseeko(FILE* fp, off_t offset, int whence) {
+ ScopedFileLock sfl(fp);
+
+ if (!__file_is_seekable(fp)) return -1;
+
+ // Change any SEEK_CUR to SEEK_SET, and check `whence' argument.
+ // After this, whence is either SEEK_SET or SEEK_END.
+ if (whence == SEEK_CUR) {
+ fpos_t current_offset = __ftello_unlocked(fp);
+ if (current_offset == -1) {
+ return EOF;
+ }
+ offset += current_offset;
+ whence = SEEK_SET;
+ } else if (whence != SEEK_SET && whence != SEEK_END) {
+ errno = EINVAL;
+ return EOF;
+ }
+
+ if (fp->_bf._base == NULL) __smakebuf(fp);
+
+ // Flush unwritten data and attempt the seek.
+ if (__sflush(fp) || (*fp->_seek)(fp->_cookie, offset, whence) == -1) {
+ return EOF;
+ }
+
+ // Success: clear EOF indicator and discard ungetc() data.
+ if (HASUB(fp)) FREEUB(fp);
+ fp->_p = fp->_bf._base;
+ fp->_r = 0;
+ /* fp->_w = 0; */ /* unnecessary (I think...) */
+ fp->_flags &= ~__SEOF;
+ return 0;
+}
+
+// TODO: _FILE_OFFSET_BITS=64.
+int fseek(FILE* fp, long offset, int whence) {
+ return fseeko(fp, offset, whence);
+}
+
+// TODO: _FILE_OFFSET_BITS=64.
+off_t ftello(FILE* fp) {
+ ScopedFileLock sfl(fp);
+ return __ftello_unlocked(fp);
+}
+
+// TODO: _FILE_OFFSET_BITS=64
+long ftell(FILE* fp) {
+ off_t offset = ftello(fp);
+ if (offset > LONG_MAX) {
+ errno = EOVERFLOW;
+ return -1;
+ }
+ return offset;
}