libbb: experimental faster string reading routines.

1 files changed, 70 insertions, 0 deletions

diff --git a/libbb/get_line_from_file.c b/libbb/get_line_from_file.c
index 3a76f49a0..7b65ced8d 100644
--- a/libbb/get_line_from_file.c
+++ b/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