From 7ac23c6f0bdf6a25f9c71be51bc29380f0614549 Mon Sep 17 00:00:00 2001
From: Lassi Kortela <lassi@lassi.io>
Date: Wed, 14 Aug 2019 13:46:50 +0300
Subject: [PATCH] Add scanner interface to "struct buf"

Can be used to easily write simple parsers in C.
---
 c/buf.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 c/buf.h | 11 +++++++++++
 2 files changed, 72 insertions(+)

diff --git a/c/buf.c b/c/buf.c
index d3cc9a7..90bb701 100644
--- a/c/buf.c
+++ b/c/buf.c
@@ -66,3 +66,64 @@ void buf_free(struct buf *buf)
     free(buf->bytes);
     free(buf);
 }
+
+int buf_scan_end(struct buf *buf) { return buf->scan >= buf->fill; }
+
+int buf_scan_byte(struct buf *buf, int byte)
+{
+    if (buf_scan_end(buf))
+        return 0;
+    if (buf->bytes[buf->scan] != byte)
+        return 0;
+    buf->scan++;
+    return 1;
+}
+
+int buf_scan_bag(struct buf *buf, const char *bag)
+{
+    if (buf_scan_end(buf))
+        return 0;
+    if (!strchr(bag, buf->bytes[buf->scan]))
+        return 0;
+    buf->scan++;
+    return 1;
+}
+
+int buf_scan_bag_not(struct buf *buf, const char *bag)
+{
+    if (buf_scan_end(buf))
+        return 0;
+    if (strchr(bag, buf->bytes[buf->scan]))
+        return 0;
+    buf->scan++;
+    return 1;
+}
+
+int buf_scan_while(struct buf *buf, const char *bag)
+{
+    if (!buf_scan_bag(buf, bag))
+        return 0;
+    while (buf_scan_bag(buf, bag))
+        ;
+    return 1;
+}
+
+int buf_scan_while_not(struct buf *buf, const char *bag)
+{
+    if (!buf_scan_bag_not(buf, bag))
+        return 0;
+    while (buf_scan_bag_not(buf, bag))
+        ;
+    return 1;
+}
+
+void buf_scan_mark(struct buf *buf) { buf->mark = buf->scan; }
+
+int buf_scan_equals(struct buf *buf, const char *s)
+{
+    if (buf->scan < buf->mark)
+        return 0;
+    if (buf->scan - buf->mark != strlen(s))
+        return 0;
+    return !!memcmp(buf->bytes + buf->mark, s, strlen(s));
+}
diff --git a/c/buf.h b/c/buf.h
index 4a00d88..bb89475 100644
--- a/c/buf.h
+++ b/c/buf.h
@@ -4,6 +4,8 @@
 struct buf {
     size_t cap;
     size_t fill;
+    size_t scan;
+    size_t mark;
     char *bytes;
 };
 
@@ -15,3 +17,12 @@ void buf_putb(struct buf *buf, const void *bytes, size_t nbyte);
 void buf_puts(struct buf *buf, const char *s);
 void buf_putu(struct buf *buf, uint64_t u);
 void buf_free(struct buf *buf);
+
+int buf_scan_end(struct buf *buf);
+int buf_scan_byte(struct buf *buf, int byte);
+int buf_scan_bag(struct buf *buf, const char *bag);
+int buf_scan_bag_not(struct buf *buf, const char *bag);
+int buf_scan_while(struct buf *buf, const char *bag);
+int buf_scan_while_not(struct buf *buf, const char *bag);
+void buf_scan_mark(struct buf *buf);
+int buf_scan_equals(struct buf *buf, const char *s);