[klibc] stdio: don't cache the file pointer

Caching the file pointer is incorrect for append streams, and if we
have to make system calls for append streams we might as well not
bother maintaining the file pointer at all... the biggest win came
from the fact the ftell() could be inlined.

A fully optimized libc can maintain the cached pointer for non-append
streams, but for klibc, don't bother maintaining the file pointer at
all, and just let the kernel worry about that.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

7 files changed, 10 insertions, 22 deletions

diff --git a/usr/include/stdio.h b/usr/include/stdio.h
index 0d4c7d890076a1..f0e81e977d5d6a 100644
--- a/usr/include/stdio.h
+++ b/usr/include/stdio.h
@@ -12,7 +12,6 @@
 #include <unistd.h>
 
 struct _IO_file {
-	off_t _IO_filepos;	/* File position */
 	int _IO_fileno;		/* Underlying file descriptor */
 	_Bool _IO_eof;		/* End of file flag */
 	_Bool _IO_error;	/* Error flag */
@@ -113,11 +112,6 @@ fwrite(const void *__p, size_t __s, size_t __n, FILE * __f)
 	return _fwrite(__p, __s * __n, __f) / __s;
 }
 
-__extern_inline off_t ftell(FILE *__f)
-{
-	return __f->_IO_filepos;
-}
-
 __extern_inline int fileno(FILE *__f)
 {
 	return __f->_IO_fileno;
diff --git a/usr/klibc/stdio/fdopen.c b/usr/klibc/stdio/fdopen.c
index 2536eb71cfaba0..a921b5910e572f 100644
--- a/usr/klibc/stdio/fdopen.c
+++ b/usr/klibc/stdio/fdopen.c
@@ -21,7 +21,6 @@ FILE *fdopen(int fd, const char *mode)
 	const size_t bufoffs =
 		(sizeof *f + 4*sizeof(void *) - 1) &
 		~(4*sizeof(void *) - 1);
-	off_t pos;
 
 	(void)mode;
 
@@ -31,8 +30,6 @@ FILE *fdopen(int fd, const char *mode)
 
 	f->data = f->buf = (char *)f + bufoffs;
 	f->pub._IO_fileno = fd;
-	pos = lseek(fd, 0, SEEK_CUR);
-	f->pub._IO_filepos = (pos >= 0) ? pos : 0;
 	f->bufsiz = BUFSIZ;
 	f->bufmode = isatty(fd) ? _IOLBF : _IOFBF;
 
diff --git a/usr/klibc/stdio/fgetc.c b/usr/klibc/stdio/fgetc.c
index 04d9ce02382a3b..a0e8650fee56e0 100644
--- a/usr/klibc/stdio/fgetc.c
+++ b/usr/klibc/stdio/fgetc.c
@@ -11,7 +11,6 @@ int fgetc(FILE *file)
 
 	if (__likely(f->ibytes)) {
 		f->ibytes--;
-		f->pub._IO_filepos++;
 		return (unsigned char) *f->data++;
 	} else {
 		return _fread(&ch, 1, file) == 1 ? ch : EOF;
diff --git a/usr/klibc/stdio/fread.c b/usr/klibc/stdio/fread.c
index caad20b40bbdc5..b0994268e7b8ef 100644
--- a/usr/klibc/stdio/fread.c
+++ b/usr/klibc/stdio/fread.c
@@ -54,7 +54,6 @@ size_t _fread(void *buf, size_t count, FILE *file)
 				p += rv;
 				bytes += rv;
 				count -= rv;
-				f->pub._IO_filepos += rv;
 			} else {
 				f->ibytes = rv;
 				f->data = rdptr;
@@ -74,7 +73,6 @@ size_t _fread(void *buf, size_t count, FILE *file)
 			count -= nb;
 			f->data += nb;
 			f->ibytes -= nb;
-			f->pub._IO_filepos += nb;
 		}
 	}
 	return bytes;
diff --git a/usr/klibc/stdio/fseek.c b/usr/klibc/stdio/fseek.c
index d352aa0c71951d..adfcbeb7a8f780 100644
--- a/usr/klibc/stdio/fseek.c
+++ b/usr/klibc/stdio/fseek.c
@@ -13,14 +13,11 @@ __extern int fseek(FILE *file, off_t where, int whence)
 		if (__fflush(f))
 			return -1;
 
-	if (whence == SEEK_CUR) {
-		where += f->pub._IO_filepos;
-		whence = SEEK_SET;
-	}
+	if (whence == SEEK_CUR)
+		where -= f->ibytes;
 
 	rv = lseek(f->pub._IO_fileno, where, whence);
 	if (__likely(rv != (off_t)-1)) {
-		f->pub._IO_filepos = rv;
 		f->pub._IO_eof = false;
 		f->ibytes = 0;
 		f->obytes = 0;
diff --git a/usr/klibc/stdio/ftell.c b/usr/klibc/stdio/ftell.c
index f3133d8709fdec..cb1202da0bc1fc 100644
--- a/usr/klibc/stdio/ftell.c
+++ b/usr/klibc/stdio/ftell.c
@@ -1,7 +1,12 @@
-#define __NO_STDIO_INLINES
 #include "stdioint.h"
 
-off_t ftell(FILE *f)
+off_t ftell(FILE *file)
 {
-	return f->_IO_filepos;
+	struct _IO_file_pvt *f = stdio_pvt(file);
+	off_t pos = lseek(f->pub._IO_fileno, 0, SEEK_CUR);
+
+	if (pos >= 0)
+		pos += (int)f->obytes - (int)f->ibytes;
+
+	return pos;
 }
diff --git a/usr/klibc/stdio/fwrite.c b/usr/klibc/stdio/fwrite.c
index 86eb3d4dac0542..d167257ea778ba 100644
--- a/usr/klibc/stdio/fwrite.c
+++ b/usr/klibc/stdio/fwrite.c
@@ -38,7 +38,6 @@ static size_t fwrite_noflush(const void *buf, size_t count,
 			p += rv;
 			bytes += rv;
 			count -= rv;
-			f->pub._IO_filepos += rv;
 		} else {
 			nb = f->bufsiz - f->obytes;
 			nb = (count < nb) ? count : nb;
@@ -48,7 +47,6 @@ static size_t fwrite_noflush(const void *buf, size_t count,
 				f->obytes += nb;
 				count -= nb;
 				bytes += nb;
-				f->pub._IO_filepos += nb;
 			}
 		}
 	}