1 files changed, 73 insertions, 0 deletions
diff --git a/lib/sbuf.h b/lib/sbuf.h
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+++ b/lib/sbuf.h
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+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Simple string buffer
+ *
+ * Copyright (C) 2017 Christian Franke
+ */
+#ifndef SBUF_H
+#define SBUF_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * sbuf provides a simple string buffer. One application where this comes
+ * in handy is the parsing of binary data: If there is an error in the parsing
+ * process due to invalid input data, printing an error message explaining what
+ * went wrong is definitely useful. However, just printing the actual error,
+ * without any information about the previous parsing steps, is usually not very
+ * helpful.
+ * Using sbuf, the parser can log the whole parsing process into a buffer using
+ * a printf like API. When an error occurs, all the information about previous
+ * parsing steps is there in the log, without any need for backtracking, and can
+ * be used to give a detailed and useful error description.
+ * When parsing completes successfully without any error, the log can just be
+ * discarded unless debugging is turned on, to not spam the log.
+ *
+ * For the described usecase, the code would look something like this:
+ *
+ * int sbuf_example(..., char **parser_log)
+ * {
+ *         struct sbuf logbuf;
+ *
+ *         sbuf_init(&logbuf, NULL, 0);
+ *         sbuf_push(&logbuf, 0, "Starting parser\n");
+ *
+ *         int rv = do_parse(&logbuf, ...);
+ *
+ *         *parser_log = sbuf_buf(&logbuf);
+ *
+ *         return 1;
+ * }
+ *
+ * In this case, sbuf_example uses a string buffer with undefined size, which
+ * will
+ * be allocated on the heap by sbuf. The caller of sbuf_example is expected to
+ * free
+ * the string returned in parser_log.
+ */
+
+#define SBUF_DEFAULT_SIZE 8192
+
+struct sbuf {
+	bool fixed;
+	char *buf;
+	size_t size;
+	size_t pos;
+	int indent;
+};
+
+void sbuf_init(struct sbuf *dest, char *buf, size_t size);
+void sbuf_reset(struct sbuf *buf);
+const char *sbuf_buf(struct sbuf *buf);
+void sbuf_free(struct sbuf *buf);
+#include "lib/log.h"
+void sbuf_push(struct sbuf *buf, int indent, const char *format, ...)
+	PRINTFRR(3, 4);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif