1 files changed, 357 insertions, 0 deletions
diff --git a/linux/printbuf.c b/linux/printbuf.c
new file mode 100644
index 0000000..3fc9ff4
--- /dev/null
+++ b/linux/printbuf.c
@@ -0,0 +1,357 @@
+// SPDX-License-Identifier: LGPL-2.1+
+/* Copyright (C) 2022 Kent Overstreet */
+
+#include <linux/err.h>
+#include <linux/math64.h>
+#include <linux/printbuf.h>
+#include <linux/slab.h>
+
+#ifdef __KERNEL__
+#include <linux/export.h>
+#include <linux/kernel.h>
+#else
+#ifndef EXPORT_SYMBOL
+#define EXPORT_SYMBOL(x)
+#endif
+#endif
+
+static inline size_t printbuf_linelen(struct printbuf *buf)
+{
+	return buf->pos - buf->last_newline;
+}
+
+int printbuf_make_room(struct printbuf *out, unsigned extra)
+{
+	unsigned new_size;
+	char *buf;
+
+	if (!out->heap_allocated)
+		return 0;
+
+	/* Reserved space for terminating nul: */
+	extra += 1;
+
+	if (out->pos + extra < out->size)
+		return 0;
+
+	new_size = roundup_pow_of_two(out->size + extra);
+	buf = krealloc(out->buf, new_size, !out->atomic ? GFP_KERNEL : GFP_NOWAIT);
+
+	if (!buf) {
+		out->allocation_failure = true;
+		return -ENOMEM;
+	}
+
+	out->buf	= buf;
+	out->size	= new_size;
+	return 0;
+}
+EXPORT_SYMBOL(printbuf_make_room);
+
+/**
+ * printbuf_str - returns printbuf's buf as a C string, guaranteed to be null
+ * terminated
+ */
+const char *printbuf_str(const struct printbuf *buf)
+{
+	/*
+	 * If we've written to a printbuf then it's guaranteed to be a null
+	 * terminated string - but if we haven't, then we might not have
+	 * allocated a buffer at all:
+	 */
+	return buf->pos
+		? buf->buf
+		: "";
+}
+EXPORT_SYMBOL(printbuf_str);
+
+/**
+ * printbuf_exit - exit a printbuf, freeing memory it owns and poisoning it
+ * against accidental use.
+ */
+void printbuf_exit(struct printbuf *buf)
+{
+	if (buf->heap_allocated) {
+		kfree(buf->buf);
+		buf->buf = ERR_PTR(-EINTR); /* poison value */
+	}
+}
+EXPORT_SYMBOL(printbuf_exit);
+
+void prt_newline(struct printbuf *buf)
+{
+	unsigned i;
+
+	printbuf_make_room(buf, 1 + buf->indent);
+
+	__prt_char(buf, '\n');
+
+	buf->last_newline	= buf->pos;
+
+	for (i = 0; i < buf->indent; i++)
+		__prt_char(buf, ' ');
+
+	printbuf_nul_terminate(buf);
+
+	buf->last_field		= buf->pos;
+	buf->tabstop = 0;
+}
+EXPORT_SYMBOL(prt_newline);
+
+/**
+ * printbuf_indent_add - add to the current indent level
+ *
+ * @buf: printbuf to control
+ * @spaces: number of spaces to add to the current indent level
+ *
+ * Subsequent lines, and the current line if the output position is at the start
+ * of the current line, will be indented by @spaces more spaces.
+ */
+void printbuf_indent_add(struct printbuf *buf, unsigned spaces)
+{
+	if (WARN_ON_ONCE(buf->indent + spaces < buf->indent))
+		spaces = 0;
+
+	buf->indent += spaces;
+	while (spaces--)
+		prt_char(buf, ' ');
+}
+EXPORT_SYMBOL(printbuf_indent_add);
+
+/**
+ * printbuf_indent_sub - subtract from the current indent level
+ *
+ * @buf: printbuf to control
+ * @spaces: number of spaces to subtract from the current indent level
+ *
+ * Subsequent lines, and the current line if the output position is at the start
+ * of the current line, will be indented by @spaces less spaces.
+ */
+void printbuf_indent_sub(struct printbuf *buf, unsigned spaces)
+{
+	if (WARN_ON_ONCE(spaces > buf->indent))
+		spaces = buf->indent;
+
+	if (buf->last_newline + buf->indent == buf->pos) {
+		buf->pos -= spaces;
+		printbuf_nul_terminate(buf);
+	}
+	buf->indent -= spaces;
+}
+EXPORT_SYMBOL(printbuf_indent_sub);
+
+/**
+ * prt_tab - Advance printbuf to the next tabstop
+ *
+ * @buf: printbuf to control
+ *
+ * Advance output to the next tabstop by printing spaces.
+ */
+void prt_tab(struct printbuf *out)
+{
+	int spaces = max_t(int, 0, out->tabstops[out->tabstop] - printbuf_linelen(out));
+
+	BUG_ON(out->tabstop > ARRAY_SIZE(out->tabstops));
+
+	prt_chars(out, ' ', spaces);
+
+	out->last_field = out->pos;
+	out->tabstop++;
+}
+EXPORT_SYMBOL(prt_tab);
+
+/**
+ * prt_tab_rjust - Advance printbuf to the next tabstop, right justifying
+ * previous output
+ *
+ * @buf: printbuf to control
+ *
+ * Advance output to the next tabstop by inserting spaces immediately after the
+ * previous tabstop, right justifying previously outputted text.
+ */
+void prt_tab_rjust(struct printbuf *buf)
+{
+	BUG_ON(buf->tabstop > ARRAY_SIZE(buf->tabstops));
+
+	if (printbuf_linelen(buf) < buf->tabstops[buf->tabstop]) {
+		unsigned move = buf->pos - buf->last_field;
+		unsigned shift = buf->tabstops[buf->tabstop] -
+			printbuf_linelen(buf);
+
+		printbuf_make_room(buf, shift);
+
+		if (buf->last_field + shift < buf->size)
+			memmove(buf->buf + buf->last_field + shift,
+				buf->buf + buf->last_field,
+				min(move, buf->size - 1 - buf->last_field - shift));
+
+		if (buf->last_field < buf->size)
+			memset(buf->buf + buf->last_field, ' ',
+			       min(shift, buf->size - buf->last_field));
+
+		buf->pos += shift;
+		printbuf_nul_terminate(buf);
+	}
+
+	buf->last_field = buf->pos;
+	buf->tabstop++;
+}
+EXPORT_SYMBOL(prt_tab_rjust);
+
+enum string_size_units {
+	STRING_UNITS_10,	/* use powers of 10^3 (standard SI) */
+	STRING_UNITS_2,		/* use binary powers of 2^10 */
+};
+static int string_get_size(u64 size, u64 blk_size,
+			   const enum string_size_units units,
+			   char *buf, int len)
+{
+	static const char *const units_10[] = {
+		"B", "kB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"
+	};
+	static const char *const units_2[] = {
+		"B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB", "ZiB", "YiB"
+	};
+	static const char *const *const units_str[] = {
+		[STRING_UNITS_10] = units_10,
+		[STRING_UNITS_2] = units_2,
+	};
+	static const unsigned int divisor[] = {
+		[STRING_UNITS_10] = 1000,
+		[STRING_UNITS_2] = 1024,
+	};
+	static const unsigned int rounding[] = { 500, 50, 5 };
+	int i = 0, j;
+	u32 remainder = 0, sf_cap;
+	char tmp[13];
+	const char *unit;
+
+	tmp[0] = '\0';
+
+	if (blk_size == 0)
+		size = 0;
+	if (size == 0)
+		goto out;
+
+	/* This is Napier's algorithm.  Reduce the original block size to
+	 *
+	 * coefficient * divisor[units]^i
+	 *
+	 * we do the reduction so both coefficients are just under 32 bits so
+	 * that multiplying them together won't overflow 64 bits and we keep
+	 * as much precision as possible in the numbers.
+	 *
+	 * Note: it's safe to throw away the remainders here because all the
+	 * precision is in the coefficients.
+	 */
+	while (blk_size >> 32) {
+		do_div(blk_size, divisor[units]);
+		i++;
+	}
+
+	while (size >> 32) {
+		do_div(size, divisor[units]);
+		i++;
+	}
+
+	/* now perform the actual multiplication keeping i as the sum of the
+	 * two logarithms */
+	size *= blk_size;
+
+	/* and logarithmically reduce it until it's just under the divisor */
+	while (size >= divisor[units]) {
+		remainder = do_div(size, divisor[units]);
+		i++;
+	}
+
+	/* work out in j how many digits of precision we need from the
+	 * remainder */
+	sf_cap = size;
+	for (j = 0; sf_cap*10 < 1000; j++)
+		sf_cap *= 10;
+
+	if (units == STRING_UNITS_2) {
+		/* express the remainder as a decimal.  It's currently the
+		 * numerator of a fraction whose denominator is
+		 * divisor[units], which is 1 << 10 for STRING_UNITS_2 */
+		remainder *= 1000;
+		remainder >>= 10;
+	}
+
+	/* add a 5 to the digit below what will be printed to ensure
+	 * an arithmetical round up and carry it through to size */
+	remainder += rounding[j];
+	if (remainder >= 1000) {
+		remainder -= 1000;
+		size += 1;
+	}
+
+	if (j) {
+		snprintf(tmp, sizeof(tmp), ".%03u", remainder);
+		tmp[j+1] = '\0';
+	}
+
+ out:
+	if (i >= ARRAY_SIZE(units_2))
+		unit = "UNK";
+	else
+		unit = units_str[units][i];
+
+	return snprintf(buf, len, "%u%s %s", (u32)size, tmp, unit);
+}
+
+/**
+ * prt_human_readable_u64 - Print out a u64 in human readable units
+ *
+ * Units of 2^10 (default) or 10^3 are controlled via @buf->si_units
+ */
+void prt_human_readable_u64(struct printbuf *buf, u64 v)
+{
+	printbuf_make_room(buf, 10);
+	buf->pos += string_get_size(v, 1, !buf->si_units,
+				    buf->buf + buf->pos,
+				    printbuf_remaining_size(buf));
+}
+EXPORT_SYMBOL(prt_human_readable_u64);
+
+/**
+ * prt_human_readable_s64 - Print out a s64 in human readable units
+ *
+ * Units of 2^10 (default) or 10^3 are controlled via @buf->si_units
+ */
+void prt_human_readable_s64(struct printbuf *buf, s64 v)
+{
+	if (v < 0)
+		prt_char(buf, '-');
+	prt_human_readable_u64(buf, abs(v));
+}
+EXPORT_SYMBOL(prt_human_readable_s64);
+
+/**
+ * prt_units_u64 - Print out a u64 according to printbuf unit options
+ *
+ * Units are either raw (default), or human reabable units (controlled via
+ * @buf->human_readable_units)
+ */
+void prt_units_u64(struct printbuf *out, u64 v)
+{
+	if (out->human_readable_units)
+		prt_human_readable_u64(out, v);
+	else
+		prt_printf(out, "%llu", v);
+}
+EXPORT_SYMBOL(prt_units_u64);
+
+/**
+ * prt_units_s64 - Print out a s64 according to printbuf unit options
+ *
+ * Units are either raw (default), or human reabable units (controlled via
+ * @buf->human_readable_units)
+ */
+void prt_units_s64(struct printbuf *out, s64 v)
+{
+	if (v < 0)
+		prt_char(out, '-');
+	prt_units_u64(out, abs(v));
+}
+EXPORT_SYMBOL(prt_units_s64);