mirror of
https://github.com/taigrr/gopher-os
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f1cf7466c7
This reverts commit 8f04deadc1f1620dbd0aaea07f04a6c7f82f58c0. The actual issue was triggered by a memory corruption due to the fact that the exception handling gate code did not preserve XMM regs.
66 lines
1.6 KiB
Go
66 lines
1.6 KiB
Go
package kfmt
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import "io"
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// ringBufferSize defines size of the ring buffer that buffers early Printf
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// output. Its default size is selected so it can buffer the contents of a
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// standard 80*25 text-mode console. The ring buffer size must always be a
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// power of 2.
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const ringBufferSize = 2048
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// ringBuffer models a ring buffer of size ringBufferSize. This buffer is used
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// for capturing the output of Printf before the tty and console systems are
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// initialized.
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type ringBuffer struct {
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buffer [ringBufferSize]byte
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rIndex, wIndex int
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}
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// Write writes len(p) bytes from p to the ringBuffer.
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func (rb *ringBuffer) Write(p []byte) (int, error) {
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for _, b := range p {
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rb.buffer[rb.wIndex] = b
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rb.wIndex = (rb.wIndex + 1) & (ringBufferSize - 1)
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if rb.rIndex == rb.wIndex {
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rb.rIndex = (rb.rIndex + 1) & (ringBufferSize - 1)
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}
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}
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return len(p), nil
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}
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// Read reads up to len(p) bytes into p. It returns the number of bytes read (0
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// <= n <= len(p)) and any error encountered.
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func (rb *ringBuffer) Read(p []byte) (n int, err error) {
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switch {
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case rb.rIndex < rb.wIndex:
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// read up to min(wIndex - rIndex, len(p)) bytes
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n = rb.wIndex - rb.rIndex
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if pLen := len(p); pLen < n {
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n = pLen
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}
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copy(p, rb.buffer[rb.rIndex:rb.rIndex+n])
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rb.rIndex += n
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return n, nil
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case rb.rIndex > rb.wIndex:
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// Read up to min(len(buf) - rIndex, len(p)) bytes
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n = len(rb.buffer) - rb.rIndex
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if pLen := len(p); pLen < n {
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n = pLen
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}
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copy(p, rb.buffer[rb.rIndex:rb.rIndex+n])
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rb.rIndex += n
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if rb.rIndex == len(rb.buffer) {
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rb.rIndex = 0
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}
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return n, nil
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default: // rIndex == wIndex
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return 0, io.EOF
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}
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}
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