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-rw-r--r--ch8/8-02_fopen-and-fillbuf.c82
-rw-r--r--ch8/8-02_syscalls.h47
-rw-r--r--ch8/syscalls.h222
3 files changed, 234 insertions, 117 deletions
diff --git a/ch8/8-02_fopen-and-fillbuf.c b/ch8/8-02_fopen-and-fillbuf.c
index e533da8..66d7336 100644
--- a/ch8/8-02_fopen-and-fillbuf.c
+++ b/ch8/8-02_fopen-and-fillbuf.c
@@ -1,8 +1,9 @@
+#include <errno.h>
+#include <string.h>
#include <fcntl.h>
-#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
-#include "8-02_syscalls.h"
+#include "syscalls.h"
/* The C Programming Language: 2nd Edition
*
@@ -14,76 +15,14 @@
*
* The resulting binary of this file (plus the custom header) runs through this
* source file in about 0.001s. However, the binary is 1KB larger.
+ *
+ * Some subsequent exercises use the same syscalls.h file created for this
+ * exercise. For this reason, the file only refers to its chapter and not
+ * specific exercises.
*/
-#define PERMS 0666
-
-int getc(FILE *);
-
-int my__fillbuf(my_FILE *fp) {
- int bufsize;
- if (fp->flags._READ == 0) {
- return EOF;
- }
- bufsize = (fp->flags._UNBUF != 0) ? 1 : BUFSIZ;
- if (fp->base == NULL) {
- if ((fp->base = (char *) calloc(bufsize, sizeof (char))) == NULL) {
- return EOF;
- }
- }
- fp->ptr = fp->base;
- fp->cnt = read(fp->fd, fp->ptr, bufsize);
- if (--fp->cnt < 0) {
- if (fp->cnt == -1) {
- fp->flags._EOF = 1;
- } else {
- fp->flags._ERR = 1;
- }
- fp->cnt = 0;
- return EOF;
- }
- return (unsigned char) *fp->ptr++;
-}
-
-my_FILE * my_fopen(char *name, char *mode) {
- int fd;
- my_FILE *fp;
- if (*mode != 'r' && *mode != 'w' && *mode != 'a') {
- return NULL;
- }
- for (fp = _iob; fp < _iob + FOPEN_MAX; fp++) {
- if (fp->flags._READ == 0 && fp->flags._WRITE == 0) {
- break;
- }
- }
- if (fp >= _iob + FOPEN_MAX) {
- return NULL;
- }
- if (*mode == 'w') {
- fd = creat(name, PERMS);
- } else if (*mode == 'a') {
- if ((fd = open(name, O_WRONLY, 0)) == -1) {
- fd = creat(name, PERMS);
- }
- lseek(fd, 0L, 2);
- } else {
- fd = open(name, O_RDONLY, 0);
- }
- if (fd == -1) {
- return NULL;
- }
- fp->fd = fd;
- fp->cnt = 0;
- if (*mode == 'r') {
- fp->flags._READ = 1;
- } else {
- fp->flags._WRITE = 1;
- }
- return fp;
-}
-
int main() {
- my_FILE *fp = my_fopen("8-02_fopen-and-fillbuf.c", "r");
+ FILE *fp = fopen("8-02_fopen-and-fillbuf.c", "r");
if (fp != NULL) {
puts("We could read the file.\n");
/* pro tip: don't declare this as 'unsigned' or you'll create an
@@ -91,9 +30,12 @@ int main() {
* half an hour on a newbie mistake like I did. :)
*/
char c;
- while ((c = my_getc(fp)) != EOF) {
+ while ((c = getc(fp)) != EOF) {
putchar(c);
}
+ /* fclose calls fflush */
+ fclose(fp);
+ fclose(stdout);
} else {
puts("Could not open file for reading.");
}
diff --git a/ch8/8-02_syscalls.h b/ch8/8-02_syscalls.h
deleted file mode 100644
index 728c5af..0000000
--- a/ch8/8-02_syscalls.h
+++ /dev/null
@@ -1,47 +0,0 @@
-/* 8-02_syscalls.h
- *
- * A simpler stdio.h to aid in exercises 8-2
- */
-
-long lseek(int fd, long offset, int origin);
-
-struct _flags {
- unsigned int _READ : 1;
- unsigned int _WRITE : 1;
- unsigned int _UNBUF : 1;
- unsigned int _EOF : 1;
- unsigned int _ERR : 1;
-} flags;
-
-typedef struct _iobuf {
- int cnt;
- char *ptr;
- char *base;
- struct _flags flags;
- int fd;
-} my_FILE;
-
-my_FILE _iob[FOPEN_MAX] = {
- /* stdin is read-only */
- { 0, (char *) 0, (char *) 0, {1, 0, 0, 0, 0}, 0 },
- /* stdout is write only */
- { 0, (char *) 0, (char *) 0, {0, 1, 0, 0, 0}, 1 },
- /* stderr is written AND not buffered */
- { 0, (char *) 0, (char *) 0, {0, 1, 1, 0, 0}, 2 }
-};
-
-#define feof(p) (((p)->flags._EOF) != 0)
-#define ferror(p) (((p)->flags._ERR) != 0)
-#define fileno(p) ((p)->fd)
-#define my_getc(p) (--(p)->cnt >= 0 ? (unsigned char) *(p)->ptr++ : my__fillbuf(p))
-#define getchar() getc(stdin)
-
-int my_fempty(struct _flags flags) {
- if (!flags._READ && !flags._WRITE && !flags._UNBUF && !flags._EOF && !flags._ERR) {
- return 1;
- } else {
- return 0;
- }
-}
-
-int my_fclose(my_FILE*);
diff --git a/ch8/syscalls.h b/ch8/syscalls.h
new file mode 100644
index 0000000..ff58db5
--- /dev/null
+++ b/ch8/syscalls.h
@@ -0,0 +1,222 @@
+/* syscalls.h
+ *
+ * A simpler stdio.h to aid in exercises within chapter 8
+ */
+
+/* Declarations */
+int puts(char *);
+long lseek(int fd, long offset, int origin);
+
+/* workarounds for GNU/Linux */
+#undef NULL
+
+#define PERMS 0666
+#define NULL 0
+#define EOF (-1)
+#define BUFSIZ 100
+#define FOPEN_MAX 20
+
+
+struct _flags {
+ unsigned int _READ : 1;
+ unsigned int _WRITE : 1;
+ unsigned int _UNBUF : 1;
+ unsigned int _EOF : 1;
+ unsigned int _ERR : 1;
+} flags;
+
+typedef struct _iobuf {
+ int cnt;
+ char *ptr;
+ char *base;
+ struct _flags flags;
+ int fd;
+} FILE;
+
+FILE _iob[FOPEN_MAX] = {
+ /* stdin is read-only */
+ { 0, (char *) 0, (char *) 0, {1, 0, 0, 0, 0}, 0 },
+ /* stdout is write only */
+ { 0, (char *) 0, (char *) 0, {0, 1, 0, 0, 0}, 1 },
+ /* stderr is written AND not buffered */
+ { 0, (char *) 0, (char *) 0, {0, 1, 1, 0, 0}, 2 }
+};
+
+#define stdin (&_iob[0])
+#define stdout (&_iob[1])
+#define stderr (&_iob[2])
+
+#define feof(p) (((p)->flags._EOF) != 0)
+#define ferror(p) (((p)->flags._ERR) != 0)
+#define fileno(p) ((p)->fd)
+
+#define getc(p) (--(p)->cnt >= 0 ? (unsigned char) *(p)->ptr++ : _fillbuf(p))
+#define putc(x,p) (--(p)->cnt >= 0 ? *(p)->ptr++ = (x) : _flushbuf((x),p))
+#define getchar() getc(stdin)
+#define putchar(x) putc((x), stdout)
+
+int fempty(struct _flags flags) {
+ if (!flags._READ && !flags._WRITE && !flags._UNBUF && !flags._EOF && !flags._ERR) {
+ return 1;
+ } else {
+ return 0;
+ }
+}
+
+FILE * fopen(char *name, char *mode) {
+ int fd;
+ FILE *fp;
+ if (*mode != 'r' && *mode != 'w' && *mode != 'a') {
+ return NULL;
+ }
+ for (fp = _iob; fp < _iob + FOPEN_MAX; fp++) {
+ if (fp->flags._READ == 0 && fp->flags._WRITE == 0) {
+ break;
+ }
+ }
+ if (fp >= _iob + FOPEN_MAX) {
+ return NULL;
+ }
+ if (*mode == 'w') {
+ fd = creat(name, PERMS);
+ } else if (*mode == 'a') {
+ if ((fd = open(name, O_WRONLY, 0)) == -1) {
+ fd = creat(name, PERMS);
+ }
+ lseek(fd, 0L, 2);
+ } else {
+ fd = open(name, O_RDONLY, 0);
+ }
+ if (fd == -1) {
+ return NULL;
+ }
+ fp->fd = fd;
+ fp->cnt = 0;
+ if (*mode == 'r') {
+ fp->flags._READ = 1;
+ } else {
+ fp->flags._WRITE = 1;
+ }
+ return fp;
+}
+
+/* int _fillbuf(FILE *); */
+
+int _fillbuf(FILE *fp) {
+ int bufsize;
+ if (fp->flags._READ == 0) {
+ return EOF;
+ }
+ bufsize = (fp->flags._UNBUF != 0) ? 1 : BUFSIZ;
+ if (fp->base == NULL) {
+ if ((fp->base = (char *) calloc(bufsize, sizeof (char))) == NULL) {
+ return EOF;
+ }
+ }
+ fp->ptr = fp->base;
+ fp->cnt = read(fp->fd, fp->ptr, bufsize);
+ if (--(fp)->cnt < 0) {
+ if (fp->cnt == -1) {
+ fp->flags._EOF = 1;
+ } else {
+ fp->flags._ERR = 1;
+ }
+ fp->cnt = 0;
+ return EOF;
+ }
+ return (unsigned char) *fp->ptr++;
+}
+
+int _cleanbuf(FILE *fp) {
+ int bufsize = (fp->flags._UNBUF != 0) ? 1 : BUFSIZ;
+ if (fp->base != NULL) {
+ free(fp->base);
+ }
+ fp->base = (char *) calloc(bufsize, sizeof (char));
+ if (fp->base == NULL) {
+ return EOF;
+ }
+ return 0;
+}
+
+/*
+ * write the buffer's contents to the file and reset the buffer
+ *
+ * Returns 0 on success, EOF on errors, with errno set.
+ */
+int _flushbuf(char c, FILE *fp) {
+ int bufsize = (fp->flags._UNBUF != 0) ? 1 : BUFSIZ;
+ if (fp->base == NULL) {
+ if (_cleanbuf(fp) != 0) {
+ errno = ENOMEM;
+ return EOF;
+ }
+ }
+ if (fp->flags._WRITE == 0) {
+ errno = EBADF;
+ return EOF;
+ }
+ int written = write(fp->fd, fp->base, bufsize);
+ if (errno > 0) {
+ fp->flags._ERR = 1;
+ strerror(errno);
+ return EOF;
+ }
+ if (_cleanbuf(fp) != 0) {
+ errno = ENOMEM;
+ return EOF;
+ }
+ fp->ptr = fp->base;
+ fp->cnt = bufsize;
+ if (c != NULL) {
+ putc(c,fp);
+ }
+ return 0;
+}
+
+int fflush(FILE *fp) {
+ if (fp == NULL) {
+ int i;
+ for (i=0; i < FOPEN_MAX; i++) {
+ /* maybe check flags and buffers? */
+ if (fp->flags._WRITE == 1) {
+ if (_flushbuf(NULL, &_iob[i]) == EOF) {
+ strerror(errno);
+ }
+ }
+ }
+ return 0;
+ }
+ if (fp->flags._WRITE == 1) {
+ if (_flushbuf(NULL, fp) == EOF) {
+ strerror(errno);
+ }
+ }
+ return 0;
+}
+
+int fclose(FILE *fp) {
+ struct _flags f = {0,0,0,0,0};
+ if (fp->flags._WRITE == 1) {
+ fflush(fp);
+ }
+ if (fp->base != NULL) {
+ free(fp->base);
+ fp->base = NULL;
+ fp->ptr = NULL;
+ }
+ fp->cnt = 0;
+ fp->flags = f;
+ close(fp->fd);
+ fp->fd = -1;
+ return 0;
+}
+
+int puts(char *s) {
+ int i;
+ for (i=0; s[i] != '\0' && s[i] != EOF; i++) {
+ putchar(s[i]);
+ }
+ putchar('\n');
+ return i;
+}

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