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AK: Fix human_readable_size corner cases

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In particular: consistent rounding and extreme values.

Before, rounding was something like 'away from 0.999...', which led to
surprising corner cases in which the value was rounded up.

Now, rounding is always 'down'.
This even works for 0xffffffff, and also for 0xffffffffffffffffULL on 64-bit.
This commit is contained in:
Ben Wiederhake 2020-08-23 00:35:36 +02:00 • committed by Andreas Kling
parent f697d35fb1
commit 0944f56181
2 changed files with 16 additions and 16 deletions
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12
AK/NumberFormat.h
View file

@ -32,10 +32,10 @@
namespace AK { namespace AK {
// FIXME: Remove this hackery once printf() supports floats. // FIXME: Remove this hackery once printf() supports floats.
static String number_string_with_one_decimal(float number, const char* suffix) static String number_string_with_one_decimal(u64 number, u32 unit, const char* suffix)
{ {
float decimals = number - (int)number; int decimal = (number % unit) * 10 / unit;
return String::format("%d.%d %s", (int)number, (int)(decimals * 10), suffix); return String::format("%llu.%d %s", number / unit, decimal, suffix);
} }
static inline String human_readable_size(size_t size) static inline String human_readable_size(size_t size)
@ -43,10 +43,10 @@ static inline String human_readable_size(size_t size)
if (size < 1 * KiB) if (size < 1 * KiB)
return String::format("%zu B", size); return String::format("%zu B", size);
if (size < 1 * MiB) if (size < 1 * MiB)
return number_string_with_one_decimal((float)size / (float)KiB, "KiB"); return number_string_with_one_decimal(size, KiB, "KiB");
if (size < 1 * GiB) if (size < 1 * GiB)
return number_string_with_one_decimal((float)size / (float)MiB, "MiB"); return number_string_with_one_decimal(size, MiB, "MiB");
return number_string_with_one_decimal((float)size / (float)GiB, "GiB"); return number_string_with_one_decimal(size, GiB, "GiB");
} }
} }

20
AK/Tests/TestNumberFormat.cpp
View file

@ -98,7 +98,7 @@ TEST_CASE(fraction_MiB)
TEST_CASE(border_MiB_GiB) TEST_CASE(border_MiB_GiB)
{ {
EXPECT_EQ(human_readable_size(1000 * MiB), "1000.0 MiB"); EXPECT_EQ(human_readable_size(1000 * MiB), "1000.0 MiB");
EXPECT_EQ(human_readable_size(1024 * MiB - 1), "1024.0 MiB"); // TODO EXPECT_EQ(human_readable_size(1024 * MiB - 1), "1023.9 MiB");
EXPECT_EQ(human_readable_size(1024 * MiB), "1.0 GiB"); EXPECT_EQ(human_readable_size(1024 * MiB), "1.0 GiB");
EXPECT_EQ(human_readable_size(1024 * MiB + 1), "1.0 GiB"); EXPECT_EQ(human_readable_size(1024 * MiB + 1), "1.0 GiB");
} }
@ -114,9 +114,9 @@ TEST_CASE(fraction_GiB)
EXPECT_EQ(human_readable_size(1154272461), "1.0 GiB"); EXPECT_EQ(human_readable_size(1154272461), "1.0 GiB");
EXPECT_EQ(human_readable_size(1181115968), "1.0 GiB"); EXPECT_EQ(human_readable_size(1181115968), "1.0 GiB");
EXPECT_EQ(human_readable_size(1181115969), "1.1 GiB"); // TODO EXPECT_EQ(human_readable_size(1181115969), "1.0 GiB");
EXPECT_EQ(human_readable_size(1181116000), "1.1 GiB"); // TODO EXPECT_EQ(human_readable_size(1181116000), "1.0 GiB");
EXPECT_EQ(human_readable_size(1181116006), "1.1 GiB"); // TODO EXPECT_EQ(human_readable_size(1181116006), "1.0 GiB");
// 1024 * 1024 * 1024 * 1.1 = 1181116006.4 // 1024 * 1024 * 1024 * 1.1 = 1181116006.4
EXPECT_EQ(human_readable_size(1181116007), "1.1 GiB"); EXPECT_EQ(human_readable_size(1181116007), "1.1 GiB");
EXPECT_EQ(human_readable_size(1202590842), "1.1 GiB"); EXPECT_EQ(human_readable_size(1202590842), "1.1 GiB");
@ -124,9 +124,9 @@ TEST_CASE(fraction_GiB)
TEST_CASE(extremes_4byte) TEST_CASE(extremes_4byte)
{ {
EXPECT_EQ(human_readable_size(0x7fffffff), "2.0 GiB"); // TODO EXPECT_EQ(human_readable_size(0x7fffffff), "1.9 GiB");
EXPECT_EQ(human_readable_size(0x80000000), "2.0 GiB"); EXPECT_EQ(human_readable_size(0x80000000), "2.0 GiB");
EXPECT_EQ(human_readable_size(0xffffffff), "4.0 GiB"); // TODO EXPECT_EQ(human_readable_size(0xffffffff), "3.9 GiB");
} }
template<int> template<int>
@ -149,10 +149,10 @@ void actual_extremes_8byte<8>()
EXPECT_EQ(human_readable_size(0x800000000ULL), "32.0 GiB"); EXPECT_EQ(human_readable_size(0x800000000ULL), "32.0 GiB");
EXPECT_EQ(human_readable_size(0x10000000000ULL), "1024.0 GiB"); EXPECT_EQ(human_readable_size(0x10000000000ULL), "1024.0 GiB");
// Ehh, too bad. // Oh yeah! These are *correct*!
EXPECT_EQ(human_readable_size(0x7fffffffffffffffULL), "-2147483648.-2147483648 GiB"); EXPECT_EQ(human_readable_size(0x7fffffffffffffffULL), "8589934591.9 GiB");
EXPECT_EQ(human_readable_size(0x8000000000000000ULL), "-2147483648.-2147483648 GiB"); EXPECT_EQ(human_readable_size(0x8000000000000000ULL), "8589934592.0 GiB");
EXPECT_EQ(human_readable_size(0xffffffffffffffffULL), "-2147483648.-2147483648 GiB"); EXPECT_EQ(human_readable_size(0xffffffffffffffffULL), "17179869183.9 GiB");
} }
TEST_CASE(extremes_8byte) TEST_CASE(extremes_8byte)