libbb: experimental faster string reading routines.

libbb/get_line_from_file.c

@@ -67,3 +67,73 @@ char* FAST_FUNC xmalloc_fgetline(FILE *file)
 
 	return c;
 }
+
+/* Faster routines (~twice as fast). +170 bytes. Unused as of 2008-07.
+ *
+ * NB: they stop at NUL byte too.
+ * Performance is important here. Think "grep 50gigabyte_file"...
+ * Iironically, grep can't use it because of NUL issue.
+ * We sorely need C lib to provide fgets which reports size!
+ */
+
+static char* xmalloc_fgets_internal(FILE *file, int *sizep)
+{
+	int len;
+	int idx = 0;
+	char *linebuf = NULL;
+
+	while (1) {
+		char *r;
+
+		linebuf = xrealloc(linebuf, idx + 0x100);
+		r = fgets(&linebuf[idx], 0x100, file);
+		if (!r) {
+			/* need to terminate in case this is error
+			 * (EOF puts NUL itself) */
+			linebuf[idx] = '\0';
+			break;
+		}
+		/* stupid. fgets knows the len, it should report it somehow */
+		len = strlen(&linebuf[idx]);
+		idx += len;
+		if (len != 0xff || linebuf[idx - 1] == '\n')
+			break;
+	}
+	*sizep = idx;
+	if (idx) {
+		/* xrealloc(linebuf, idx + 1) is up to caller */
+		return linebuf;
+	}
+	free(linebuf);
+	return NULL;
+}
+
+/* Get line, remove trailing \n */
+char* FAST_FUNC xmalloc_fgetline_fast(FILE *file)
+{
+	int sz;
+	char *r = xmalloc_fgets_internal(file, &sz);
+	if (r && r[sz - 1] == '\n')
+		r[--sz] = '\0';
+	return r; /* not xrealloc(r, sz + 1)! */
+}
+
+#if 0
+char* FAST_FUNC xmalloc_fgets(FILE *file)
+{
+	int sz;
+	return xmalloc_fgets_internal(file, &sz);
+}
+
+/* Get line, remove trailing \n */
+char* FAST_FUNC xmalloc_fgetline(FILE *file)
+{
+	int sz;
+	char *r = xmalloc_fgets_internal(file, &sz);
+	if (!r)
+		return r;
+	if (r[sz - 1] == '\n')
+		r[--sz] = '\0';
+	return xrealloc(r, sz + 1);
+}
+#endif