Changeset bd5414e in mainline

Timestamp:

2015-09-21T21:05:26Z (9 years ago)

Author:

Jiri Svoboda <jiri@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

c70703a

Parents:

bea710f

Message:

Proper ungetc() in libc.

Location:

uspace/lib

Files:

• c/generic/io/io.c (modified) (6 diffs)
• c/generic/private/stdio.h (modified) (2 diffs)
• c/include/stdio.h (modified) (1 diff)
• posix/source/stdio.c (modified) (1 diff)

uspace/lib/c/generic/io/io.c

@@ -64 +64 @@
         .buf_head = NULL,
         .buf_tail = NULL,
-        .buf_state = _bs_empty
+        .buf_state = _bs_empty,
 };
 
@@ -466 +466 @@
                 return 0;
 
+        bytes_left = size * nmemb;
+        total_read = 0;
+        dp = (uint8_t *) dest;
+
+        /* Bytes from ungetc() buffer */
+        while (stream->ungetc_chars > 0 && bytes_left > 0) {
+                *dp++ = stream->ungetc_buf[--stream->ungetc_chars];
+                ++total_read;
+        }
+
         /* If not buffered stream, read in directly. */
         if (stream->btype == _IONBF) {
-                now = _fread(dest, size, nmemb, stream);
-                return now;
+                total_read += _fread(dest, 1, bytes_left, stream);
+                return total_read / size;
         }
 
@@ -481 +491 @@
                         return 0; /* Errno set by _fallocbuf(). */
         }
-
-        bytes_left = size * nmemb;
-        total_read = 0;
-        dp = (uint8_t *) dest;
 
         while ((!stream->error) && (!stream->eof) && (bytes_left > 0)) {
@@ -674 +680 @@
 }
 
+int ungetc(int c, FILE *stream)
+{
+        if (c == EOF)
+                return EOF;
+
+        if (stream->ungetc_chars >= UNGETC_MAX)
+                return EOF;
+
+        stream->ungetc_buf[stream->ungetc_chars++] =
+            (uint8_t)c;
+
+        stream->eof = false;
+        return (uint8_t)c;
+}
+
 int fseek(FILE *stream, off64_t offset, int whence)
 {
@@ -679 +700 @@
 
         _fflushbuf(stream);
+        stream->ungetc_chars = 0;
 
         rc = lseek(stream->fd, offset, whence);
@@ -693 +715 @@
 {
         _fflushbuf(stream);
-        return lseek(stream->fd, 0, SEEK_CUR);
+        return lseek(stream->fd, 0, SEEK_CUR) - stream->ungetc_chars;
 }
 

uspace/lib/c/generic/private/stdio.h

@@ -39 +39 @@
 #include <stdio.h>
 #include <async.h>
+
+/** Maximum characters that can be pushed back by ungetc() */
+#define UNGETC_MAX 1
 
 struct _IO_FILE {
@@ -82 +85 @@
         /** Points to end of occupied space when in read mode. */
         uint8_t *buf_tail;
+
+        /** Pushed back characters */
+        uint8_t ungetc_buf[UNGETC_MAX];
+
+        /** Number of pushed back characters */
+        int ungetc_chars;
 };
 

uspace/lib/c/include/stdio.h

@@ -109 +109 @@
 extern int puts(const char *);
 
+extern int ungetc(int, FILE *);
+
 /* Formatted string output functions */
 extern int fprintf(FILE *, const char*, ...)

uspace/lib/posix/source/stdio.c

@@ -118 +118 @@
 int posix_ungetc(int c, FILE *stream)
 {
-        uint8_t b = (uint8_t) c;
-
-        bool can_unget =
-            /* Provided character is legal. */
-            c != EOF &&
-            /* Stream is consistent. */
-            !stream->error &&
-            /* Stream is buffered. */
-            stream->btype != _IONBF &&
-            /* Last operation on the stream was a read operation. */
-            stream->buf_state == _bs_read &&
-            /* Stream buffer is already allocated (i.e. there was already carried
-             * out either write or read operation on the stream). This is probably
-             * redundant check but let's be safe. */
-            stream->buf != NULL &&
-            /* There is still space in the stream to retreat. POSIX demands the
-             * possibility to unget at least 1 character. It should be always
-             * possible, assuming the last operation on the stream read at least 1
-             * character, because the buffer is refilled in the lazily manner. */
-            stream->buf_tail > stream->buf;
-
-        if (can_unget) {
-                --stream->buf_tail;
-                stream->buf_tail[0] = b;
-                stream->eof = false;
-                return (int) b;
-        } else {
-                return EOF;
-        }
+        return ungetc(c, stream);
 }