blob: 3e0e4f7a1969df2b100025941b193274d39e4438 [file] [log] [blame]
// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <assert.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <zircon/assert.h>
#include <pretty/sizes.h>
char* format_size_fixed(char* str, size_t str_size, size_t bytes, char unit) {
static const char units[] = "BkMGTPE";
static int num_units = sizeof(units) - 1;
if (str_size == 0) {
// Even if NULL.
return str;
}
ZX_DEBUG_ASSERT(str != NULL);
if (str_size == 1) {
str[0] = '\0';
return str;
}
char* orig_str = str;
size_t orig_bytes = bytes;
retry:;
int ui = 0;
uint16_t r = 0;
bool whole = true;
// If we have a fixed (non-zero) unit, divide until we hit it.
//
// Otherwise, divide until we reach a unit that can express the value
// with 4 or fewer whole digits.
// - If we can express the value without a fraction (it's a whole
// kibi/mebi/gibibyte), use the largest possible unit (e.g., favor
// "1M" over "1024k").
// - Otherwise, favor more whole digits to retain precision (e.g.,
// favor "1025k" or "1025.0k" over "1.0M").
while (unit != 0 ? units[ui] != unit : (bytes >= 10000 || (bytes != 0 && (bytes & 1023) == 0))) {
ui++;
if (ui >= num_units) {
// We probably got an unknown unit. Fall back to a natural unit,
// but leave a hint that something's wrong.
ZX_DEBUG_ASSERT(str_size > 1);
*str++ = '?';
str_size--;
unit = 0;
bytes = orig_bytes;
goto retry;
}
if (bytes & 1023) {
whole = false;
}
r = bytes % 1024;
bytes /= 1024;
}
if (whole) {
snprintf(str, str_size, "%zu%c", bytes, units[ui]);
} else {
// r represents the remainder of the most recent division operation.
// Since we provide a single unit of precision, we can round it based
// on the second digit and increment bytes in the case that it pushes
// the final value back over into a whole number.
unsigned int round_up = ((r % 100) >= 50);
r = (r / 100) + round_up;
if (r == 10) {
bytes++;
r = 0;
}
snprintf(str, str_size, "%zu.%1u%c", bytes, r, units[ui]);
}
return orig_str;
}
char* format_size(char* str, size_t str_size, size_t bytes) {
return format_size_fixed(str, str_size, bytes, 0);
}