table-based token scanner: implemented tbnf_scan_token(), tbnf_scan_tokens().

1 files changed, 102 insertions, 0 deletions

diff --git a/src/tokscan/tbnf_scan_token.c b/src/tokscan/tbnf_scan_token.c
new file mode 100644
index 0000000..b546959
--- /dev/null
+++ b/src/tokscan/tbnf_scan_token.c
@@ -0,0 +1,102 @@
+/**************************************************************/
+/*  treebnf: a tree oriented bnf library                      */
+/*  Copyright (C) 2024  SysDeer Technologies, LLC             */
+/*  Released under GPLv2 and GPLv3; see COPYING.TREEBNF.      */
+/**************************************************************/
+
+#include <treebnf/treebnf.h>
+
+#define TBNF_STATE_STACK_SIZE   (512)
+
+/* single token, read-only context */
+int tbnf_scan_token(const struct tbnf_scan_ctx * sctx, struct tbnf_token * tok)
+{
+	int ret  = 0;
+	int len  = 0;
+	int type = 0;
+
+	int tidx = 0;
+	int sidx = sctx->tok_scan_state;
+
+	for (; tidx < sctx->tok_scan_nents; ) {
+		if (sctx->tok_scan_tbls[sidx][tidx].tok_scan_fn)
+			ret = sctx->tok_scan_tbls[sidx][tidx].tok_scan_fn(sctx);
+
+		if (ret > len) {
+			len  = ret;
+			type = tidx;
+		}
+
+		tidx++;
+	}
+
+	tok->tok_type = type;
+	tok->tok_len  = len;
+	tok->tok_off  = sctx->tok_scan_mark - sctx->tok_scan_base;
+
+	return (len > 0) ? 0 : -1;
+}
+
+/* scan up to ntoks tokens, read-write context */
+int tbnf_scan_tokens(struct tbnf_scan_ctx * sctx, size_t ntoks, struct tbnf_token * tokv, int any)
+{
+	int                     ret;
+	int *                   state;
+	int *                   stcap;
+	int                     ststk[TBNF_STATE_STACK_SIZE];
+	struct tbnf_scan_tbl *  pentry;
+
+	ret      = 0;
+	ntoks    = (ntoks > INT32_MAX) ? INT32_MAX : ntoks;
+
+	state    = ststk;
+	state[0] = sctx->tok_scan_state;
+
+	stcap    = &state[TBNF_STATE_STACK_SIZE];
+	stcap--;
+
+	/*******************************************************************/
+	/* a positive return value that's smaller than the original ntoks, */
+	/* in combination with mark < cap, indicates an error while trying */
+	/* to obtain the next token.                                       */
+	/*******************************************************************/
+
+	for (; ntoks && (sctx->tok_scan_mark < sctx->tok_scan_cap); ) {
+		if (tbnf_scan_token(sctx,tokv) < 0)
+			return (ret > 0) ? ret : (-1);
+
+		pentry = &sctx->tok_scan_tbls[*state][tokv->tok_type];
+
+		switch (pentry->tok_state_op) {
+			case TBNF_STATE_POP:
+				if (state == ststk)
+					return (-1);
+
+				state--;
+				sctx->tok_scan_state = *state;
+				break;
+
+			case TBNF_STATE_KEEP:
+				break;
+
+			case TBNF_STATE_PUSH:
+				if (state == stcap)
+					return (-1);
+
+				sctx->tok_scan_state = pentry->tok_state_next;
+				*++state             = sctx->tok_scan_state;
+				break;
+		}
+
+		sctx->tok_scan_type  = tokv->tok_type;
+		sctx->tok_scan_mark += tokv->tok_len;
+
+		tokv->tok_any = any;
+		tokv++;
+
+		ntoks--;
+		ret++;
+	}
+
+	return ret;
+}