From ae7810f56e1daa1d2e35c06969c26835c1ed7800 Mon Sep 17 00:00:00 2001
From: midipix <writeonce@midipix.org>
Date: Wed, 15 May 2024 19:28:39 +0000
Subject: table-based token scanner: implemented tbnf_scan_token(),
 tbnf_scan_tokens().

---
 include/treebnf/treebnf.h     |   4 ++
 project/common.mk             |   1 +
 project/tree.mk               |   1 +
 src/tokscan/tbnf_scan_token.c | 102 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 108 insertions(+)
 create mode 100644 src/tokscan/tbnf_scan_token.c

diff --git a/include/treebnf/treebnf.h b/include/treebnf/treebnf.h
index 1a8db27..a5c0359 100644
--- a/include/treebnf/treebnf.h
+++ b/include/treebnf/treebnf.h
@@ -163,6 +163,10 @@ tbnf_api int  tbnf_lib_map_raw_input    (const struct tbnf_driver_ctx *,
 
 tbnf_api int  tbnf_lib_unmap_raw_input  (struct tbnf_raw_input *);
 
+/* table-based token scanner api */
+tbnf_api int  tbnf_scan_token           (const struct tbnf_scan_ctx *, struct tbnf_token *);
+tbnf_api int  tbnf_scan_tokens          (struct tbnf_scan_ctx *, size_t ntoks, struct tbnf_token *, int any);
+
 /* utility api */
 tbnf_api int  tbnf_main                 (char **, char **,
                                          const struct tbnf_fd_ctx *);
diff --git a/project/common.mk b/project/common.mk
index 7a77195..c9523bd 100644
--- a/project/common.mk
+++ b/project/common.mk
@@ -5,6 +5,7 @@ API_SRCS = \
 	src/driver/tbnf_unit_ctx.c      \
 	src/output/tbnf_output_error.c  \
 	src/skin/tbnf_skin_default.c    \
+	src/tokscan/tbnf_scan_token.c   \
 
 INTERNAL_SRCS = \
 	src/internal/$(PACKAGE)_dprintf_impl.c \
diff --git a/project/tree.mk b/project/tree.mk
index f3ae848..0c51986 100644
--- a/project/tree.mk
+++ b/project/tree.mk
@@ -2,6 +2,7 @@ TREE_DIRS = 	src          \
 		src/driver   \
 		src/output   \
 		src/skin     \
+		src/tokscan  \
 		src/internal \
 
 tree.tag:
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;
+}
-- 
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