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std: Make windows.ReadFile allow short reads

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Make it behave like the read() wrapper for unix systems.
Reading the whole buffer breaks some use-cases like buffered readers
over sockets.

Closes #7121
This commit is contained in:
LemonBoy 2020-11-16 10:37:23 +01:00 committed by Andrew Kelley
parent 6e2e747b0b
commit 36c869dc14
1 changed files with 8 additions and 11 deletions
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19
lib/std/os/windows.zig
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@ -442,33 +442,30 @@ pub fn ReadFile(in_hFile: HANDLE, buffer: []u8, offset: ?u64, io_mode: std.io.Mo
}
return @as(usize, bytes_transferred);
} else {
var index: usize = 0;
while (index < buffer.len) {
const want_read_count = @intCast(DWORD, math.min(@as(DWORD, maxInt(DWORD)), buffer.len - index));
while (true) {
const want_read_count = @intCast(DWORD, math.min(@as(DWORD, maxInt(DWORD)), buffer.len));
var amt_read: DWORD = undefined;
var overlapped_data: OVERLAPPED = undefined;
const overlapped: ?*OVERLAPPED = if (offset) |off| blk: {
overlapped_data = .{
.Internal = 0,
.InternalHigh = 0,
.Offset = @truncate(u32, off + index),
.OffsetHigh = @truncate(u32, (off + index) >> 32),
.Offset = @truncate(u32, off),
.OffsetHigh = @truncate(u32, off >> 32),
.hEvent = null,
};
break :blk &overlapped_data;
} else null;
if (kernel32.ReadFile(in_hFile, buffer.ptr + index, want_read_count, &amt_read, overlapped) == 0) {
if (kernel32.ReadFile(in_hFile, buffer.ptr, want_read_count, &amt_read, overlapped) == 0) {
switch (kernel32.GetLastError()) {
.OPERATION_ABORTED => continue,
.BROKEN_PIPE => return index,
.HANDLE_EOF => return index,
.BROKEN_PIPE => return 0,
.HANDLE_EOF => return 0,
else => |err| return unexpectedError(err),
}
}
if (amt_read == 0) return index;
index += amt_read;
return amt_read;
}
return index;
}
}