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Remove unsafe code from StringParser #125640

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Remove unsafe code from StringParser #125640

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dd5276b
Remove unsafe code from StringParser
EgorBo Mar 17, 2026
4fe274f
Hoist fields to locals in StringParser parse methods
EgorBo Mar 17, 2026
b74e457
Address PR feedback: use ReadOnlySpan for bounds-check elimination an…
EgorBo Mar 17, 2026
a74125c
Fix empty-component test: remove extra MoveNextOrFail, add default br…
EgorBo Mar 17, 2026
c5b7d94
Update StringParserTests.cs
EgorBo Mar 17, 2026
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144 changes: 67 additions & 77 deletions src/libraries/Common/src/System/IO/StringParser.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -134,147 +134,137 @@ public string ExtractCurrent()
}

/// <summary>Moves to the next component and parses it as an Int32.</summary>
public unsafe int ParseNextInt32()
public int ParseNextInt32()
{
MoveNextOrFail();

int startIndex = _startIndex;
int endIndex = _endIndex;
ReadOnlySpan<char> span = _buffer.AsSpan(startIndex, endIndex - startIndex);

if (span.IsEmpty)
{
ThrowForInvalidData();
}
Comment on lines +141 to +148

bool negative = false;
int result = 0;
int i = 0;

fixed (char* bufferPtr = _buffer)
if (span[0] == '-')
{
char* p = bufferPtr + _startIndex;
char* end = bufferPtr + _endIndex;

if (p == end)
negative = true;
i = 1;
if (i == span.Length)
{
ThrowForInvalidData();
}
}

if (*p == '-')
{
negative = true;
p++;
if (p == end)
{
ThrowForInvalidData();
}
}

while (p != end)
for (; i < span.Length; i++)
{
int d = span[i] - '0';
if (d < 0 || d > 9)
{
int d = *p - '0';
if (d < 0 || d > 9)
{
ThrowForInvalidData();
}
result = negative ? checked((result * 10) - d) : checked((result * 10) + d);

p++;
ThrowForInvalidData();
}
result = negative ? checked((result * 10) - d) : checked((result * 10) + d);
}

Debug.Assert(result == int.Parse(ExtractCurrent()), "Expected manually parsed result to match Parse result");
return result;
}

/// <summary>Moves to the next component and parses it as an Int64.</summary>
public unsafe long ParseNextInt64()
public long ParseNextInt64()
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@tannergooding tannergooding Mar 17, 2026

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Do we know why this is its own custom handler and not just reusing the shared number parsing code used by int/long?

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@stephentoub stephentoub Mar 17, 2026 •
edited
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When this was written, span didn't exist yet, and we didn't want to allocate strings for each component just to be able to parse them. Now that span exists and you can int/long.Parse from them, that should be doable.

{
MoveNextOrFail();

int startIndex = _startIndex;
int endIndex = _endIndex;
ReadOnlySpan<char> span = _buffer.AsSpan(startIndex, endIndex - startIndex);

if (span.IsEmpty)
{
ThrowForInvalidData();
}

bool negative = false;
long result = 0;
int i = 0;

fixed (char* bufferPtr = _buffer)
if (span[0] == '-')
{
char* p = bufferPtr + _startIndex;
char* end = bufferPtr + _endIndex;

if (p == end)
negative = true;
i = 1;
if (i == span.Length)
{
ThrowForInvalidData();
}
}

if (*p == '-')
{
negative = true;
p++;
if (p == end)
{
ThrowForInvalidData();
}
}

while (p != end)
for (; i < span.Length; i++)
{
int d = span[i] - '0';
if (d < 0 || d > 9)
{
int d = *p - '0';
if (d < 0 || d > 9)
{
ThrowForInvalidData();
}
result = negative ? checked((result * 10) - d) : checked((result * 10) + d);

p++;
ThrowForInvalidData();
}
result = negative ? checked((result * 10) - d) : checked((result * 10) + d);
}

Debug.Assert(result == long.Parse(ExtractCurrent()), "Expected manually parsed result to match Parse result");
return result;
}

/// <summary>Moves to the next component and parses it as a UInt32.</summary>
public unsafe uint ParseNextUInt32()
public uint ParseNextUInt32()
{
MoveNextOrFail();
if (_startIndex == _endIndex)

ReadOnlySpan<char> span = _buffer.AsSpan(_startIndex, _endIndex - _startIndex);

if (span.IsEmpty)
{
ThrowForInvalidData();
}

uint result = 0;
fixed (char* bufferPtr = _buffer)
for (int i = 0; i < span.Length; i++)
{
char* p = bufferPtr + _startIndex;
char* end = bufferPtr + _endIndex;
while (p != end)
int d = span[i] - '0';
if (d < 0 || d > 9)
{
int d = *p - '0';
if (d < 0 || d > 9)
{
ThrowForInvalidData();
}
result = (uint)checked((result * 10) + d);

p++;
ThrowForInvalidData();
}
result = (uint)checked((result * 10) + d);
}

Debug.Assert(result == uint.Parse(ExtractCurrent()), "Expected manually parsed result to match Parse result");
return result;
}

/// <summary>Moves to the next component and parses it as a UInt64.</summary>
public unsafe ulong ParseNextUInt64()
public ulong ParseNextUInt64()
{
MoveNextOrFail();

ReadOnlySpan<char> span = _buffer.AsSpan(_startIndex, _endIndex - _startIndex);

if (span.IsEmpty)
{
ThrowForInvalidData();
}

ulong result = 0;
fixed (char* bufferPtr = _buffer)
for (int i = 0; i < span.Length; i++)
{
char* p = bufferPtr + _startIndex;
char* end = bufferPtr + _endIndex;
while (p != end)
int d = span[i] - '0';
if (d < 0 || d > 9)
{
int d = *p - '0';
if (d < 0 || d > 9)
{
ThrowForInvalidData();
}
result = checked((result * 10ul) + (ulong)d);

p++;
ThrowForInvalidData();
}
result = checked((result * 10ul) + (ulong)d);
}

Debug.Assert(result == ulong.Parse(ExtractCurrent()), "Expected manually parsed result to match Parse result");
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