ee7c276493
* Use 64-bit integers on 64-bit platforms, just like gc and gccgo: https://golang.org/doc/go1.1#int * Do not use a separate length type. Instead, use uintptr everywhere a length is expected.
53 строки
1,5 КиБ
Go
53 строки
1,5 КиБ
Go
package runtime
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// This file implements compiler builtins for slices: append() and copy().
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import (
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"unsafe"
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)
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// Builtin append(src, elements...) function: append elements to src and return
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// the modified (possibly expanded) slice.
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func sliceAppend(srcBuf, elemsBuf unsafe.Pointer, srcLen, srcCap, elemsLen uintptr, elemSize uintptr) (unsafe.Pointer, uintptr, uintptr) {
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if elemsLen == 0 {
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// Nothing to append, return the input slice.
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return srcBuf, srcLen, srcCap
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}
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if srcLen+elemsLen > srcCap {
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// Slice does not fit, allocate a new buffer that's large enough.
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srcCap = srcCap * 2
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if srcCap == 0 { // e.g. zero slice
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srcCap = 1
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}
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for srcLen+elemsLen > srcCap {
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// This algorithm may be made more memory-efficient: don't multiply
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// by two but by 1.5 or something. As far as I can see, that's
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// allowed by the Go language specification (but may be observed by
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// programs).
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srcCap *= 2
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}
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buf := alloc(srcCap * elemSize)
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// Copy the old slice to the new slice.
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if srcLen != 0 {
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memmove(buf, srcBuf, srcLen*elemSize)
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}
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srcBuf = buf
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}
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// The slice fits (after possibly allocating a new one), append it in-place.
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memmove(unsafe.Pointer(uintptr(srcBuf)+srcLen*elemSize), elemsBuf, elemsLen*elemSize)
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return srcBuf, srcLen + elemsLen, srcCap
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}
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// Builtin copy(dst, src) function: copy bytes from dst to src.
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func sliceCopy(dst, src unsafe.Pointer, dstLen, srcLen uintptr, elemSize uintptr) uintptr {
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// n = min(srcLen, dstLen)
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n := srcLen
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if n > dstLen {
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n = dstLen
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}
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memmove(dst, src, n*elemSize)
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return n
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}
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