1 files changed, 119 insertions, 0 deletions
diff --git a/include/linux/printbuf.h b/include/linux/printbuf.h
new file mode 100644
index 000000000000..2ec1d6045ee1
--- /dev/null
+++ b/include/linux/printbuf.h
@@ -0,0 +1,119 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+/* Copyright (C) 2022 Kent Overstreet */
+
+#ifndef _LINUX_PRINTBUF_H
+#define _LINUX_PRINTBUF_H
+
+#include <linux/kernel.h>
+#include <linux/string.h>
+
+/*
+ * Printbufs: String buffer for outputting (printing) to, for vsnprintf
+ */
+
+struct printbuf {
+	char			*buf;
+	unsigned		size;
+	unsigned		pos;
+};
+
+/*
+ * Returns size remaining of output buffer:
+ */
+static inline unsigned printbuf_remaining_size(struct printbuf *out)
+{
+	return out->pos < out->size ? out->size - out->pos : 0;
+}
+
+/*
+ * Returns number of characters we can print to the output buffer - i.e.
+ * excluding the terminating nul:
+ */
+static inline unsigned printbuf_remaining(struct printbuf *out)
+{
+	return out->pos < out->size ? out->size - out->pos - 1 : 0;
+}
+
+static inline unsigned printbuf_written(struct printbuf *out)
+{
+	return min(out->pos, out->size);
+}
+
+/*
+ * Returns true if output was truncated:
+ */
+static inline bool printbuf_overflowed(struct printbuf *out)
+{
+	return out->pos >= out->size;
+}
+
+static inline void printbuf_nul_terminate(struct printbuf *out)
+{
+	if (out->pos < out->size)
+		out->buf[out->pos] = 0;
+	else if (out->size)
+		out->buf[out->size - 1] = 0;
+}
+
+static inline void __prt_chars(struct printbuf *out, char c, unsigned n)
+{
+	memset(out->buf + out->pos,
+	       c,
+	       min(n, printbuf_remaining(out)));
+	out->pos += n;
+}
+
+static inline void prt_chars(struct printbuf *out, char c, unsigned n)
+{
+	__prt_chars(out, c, n);
+	printbuf_nul_terminate(out);
+}
+
+static inline void __prt_char(struct printbuf *out, char c)
+{
+	if (printbuf_remaining(out))
+		out->buf[out->pos] = c;
+	out->pos++;
+}
+
+static inline void prt_char(struct printbuf *out, char c)
+{
+	__prt_char(out, c);
+	printbuf_nul_terminate(out);
+}
+
+static inline void prt_bytes(struct printbuf *out, const void *b, unsigned n)
+{
+	memcpy(out->buf + out->pos,
+	       b,
+	       min(n, printbuf_remaining(out)));
+	out->pos += n;
+	printbuf_nul_terminate(out);
+}
+
+static inline void prt_str(struct printbuf *out, const char *str)
+{
+	prt_bytes(out, str, strlen(str));
+}
+
+static inline void prt_hex_byte(struct printbuf *out, u8 byte)
+{
+	__prt_char(out, hex_asc_hi(byte));
+	__prt_char(out, hex_asc_lo(byte));
+	printbuf_nul_terminate(out);
+}
+
+static inline void prt_hex_byte_upper(struct printbuf *out, u8 byte)
+{
+	__prt_char(out, hex_asc_upper_hi(byte));
+	__prt_char(out, hex_asc_upper_lo(byte));
+	printbuf_nul_terminate(out);
+}
+
+#define PRINTBUF_EXTERN(_buf, _size)			\
+((struct printbuf) {					\
+	.buf	= _buf,					\
+	.size	= _size,				\
+})
+
+#endif /* _LINUX_PRINTBUF_H */