user/libc: fseek + ftell for getting a file's size

4 files changed, 45 insertions, 14 deletions

diff --git a/src/user/app/vterm/font.c b/src/user/app/vterm/font.c
index d9a4e3c..5a9dd24 100644
--- a/src/user/app/vterm/font.c
+++ b/src/user/app/vterm/font.c
@@ -13,13 +13,24 @@ void font_load(const char *path) {
 		exit(1);
 	}
 
-	const size_t cap = 8 * 1024; // TODO get file size
-	void *buf = malloc(cap);
+	void *buf;
+	long buflen;
+
+	fseek(f, 0, SEEK_END);
+	buflen = ftell(f);
+	if (buflen < 0) {
+		eprintf("can't get the size of \"%s\"", path);
+		exit(1);
+	}
+
+	buf = malloc(buflen);
 	if (!buf) {
 		eprintf("out of memory");
 		exit(1);
 	}
-	fread(buf, 1, cap, f);
+
+	fseek(f, 0, SEEK_SET);
+	fread(buf, 1, buflen, f);
 	if (ferror(f)) {
 		eprintf("error reading file");
 		exit(1);
diff --git a/src/user/lib/elfload.c b/src/user/lib/elfload.c
index e3853ba..7c84f45 100644
--- a/src/user/lib/elfload.c
+++ b/src/user/lib/elfload.c
@@ -9,11 +9,17 @@
 #include <user/lib/elfload.h>
 
 void elf_execf(FILE *f, char **argv, char **envp) {
-	const size_t cap = 0x60000;
-	size_t pos = 0;
-	void *buf = malloc(cap); // TODO a way to get file size
+	void *buf;
+	long buflen;
 
-	if (buf && fread(buf, 1, cap - pos, f))
+	fseek(f, 0, SEEK_END);
+	buflen = ftell(f);
+	if (buflen < 0) return; /* errno set by fseek */
+	buf = malloc(buflen);
+
+	// TODO don't read the entire file into memory
+	fseek(f, 0, SEEK_SET);
+	if (buf && fread(buf, 1, buflen, f))
 		elf_exec(buf, argv, envp);
 	free(buf);
 }
diff --git a/src/user/lib/file.c b/src/user/lib/file.c
index 84242b2..942b522 100644
--- a/src/user/lib/file.c
+++ b/src/user/lib/file.c
@@ -175,31 +175,44 @@ int fseek(FILE *f, long offset, int whence) {
 	if (fflush(f))
 		return -1;
 
+	long base;
 	switch (whence) {
 		case SEEK_SET:
-			f->pos = 0;
+			base = 0;
 			break;
 		case SEEK_CUR:
+			base = f->pos;
 			break;
 		case SEEK_END:
-			f->pos = -1;
+			base = _syscall_getsize(f->fd);
+			if (base < 0)
+				base = -1;
 			break;
 		default:
 			errno = EINVAL;
 			return -1;
 	}
 
-	bool pos_neg = f->pos < 0;
-	f->pos += offset;
-	if (pos_neg && f->pos >= 0) {
-		// TODO getting the file size
-		errno = ENOSYS;
+	if (base >= 0 && base + offset < 0) {
+		/* underflow */
+		errno = EINVAL;
+		return -1;
+	} else if (base < 0 && base + offset >= 0) {
+		/* overflow - went from a negative offset (relative to EOF)
+		 *            to a positive offset (from start of file).
+		 *            can only happen when getsize() is unsupported */
+		errno = EINVAL;
 		return -1;
 	}
+	f->pos = base + offset;
 	f->eof = false;
 	return 0;
 }
 
+long ftell(FILE *f) {
+	return f->pos;
+}
+
 int fclose(FILE *f) {
 	fflush(f);
 	if (f->fd > 0) close(f->fd);
diff --git a/src/user/lib/include/stdio.h b/src/user/lib/include/stdio.h
index 74c5230..063c81f 100644
--- a/src/user/lib/include/stdio.h
+++ b/src/user/lib/include/stdio.h
@@ -33,6 +33,7 @@ size_t fread(void *restrict ptr, size_t size, size_t nitems, FILE *restrict);
 size_t fwrite(const void *restrict ptr, size_t size, size_t nitems, FILE *restrict);
 char *fgets(char *buf, int size, FILE *f);
 int fseek(FILE *f, long offset, int whence);
+long ftell(FILE *f);
 
 int feof(FILE *);
 int ferror(FILE *);