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98 lines
2.1 KiB
98 lines
2.1 KiB
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#include <stdlib.h>
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// Caricature of folly::basic_fbstring without the union between small
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// and medium/large data representations, and with an explicit field
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// for category_ instead of bitmasking part of the data value.
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// ref:
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// https://github.com/facebook/folly/blob/72850c2ebfb94d87bea74d89fcf79f3aaa91a627/folly/FBString.h
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enum category {
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small = 0, // ignore small strings for now
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medium = 1,
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large = 2,
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};
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void* checkedMalloc(size_t size) {
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void* ptr = malloc(size);
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if (ptr == nullptr) {
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exit(1);
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}
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return ptr;
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}
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struct LikeFBString {
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int category_;
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char* buffer_;
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size_t size_;
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unsigned int* refcount_;
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LikeFBString() {}
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LikeFBString(const LikeFBString& src) {
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category_ = src.category();
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switch (src.category_) {
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case medium:
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copyMedium(src);
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break;
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case large:
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copyLarge(src);
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break;
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default:
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exit(2);
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}
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}
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~LikeFBString() {
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if (category() == medium) {
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free(buffer_);
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} else {
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decr_ref_count();
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}
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}
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void copySmall(const LikeFBString& src) {}
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void copyMedium(const LikeFBString& src) {
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buffer_ = (char*)checkedMalloc(src.size_);
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size_ = src.size_;
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}
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void copyLarge(const LikeFBString& src) {
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buffer_ = src.buffer_;
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size_ = src.size_;
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refcount_ = src.refcount_;
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*refcount_ = *refcount_ + 1;
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}
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int category() const { return category_; }
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void decr_ref_count() {
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if (*refcount_ <= 0) {
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exit(1);
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}
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*refcount_ = *refcount_ - 1;
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if (*refcount_ == 0) {
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free(buffer_);
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}
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}
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};
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void copy_fbstring(LikeFBString& s) {
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// this might alias the underlying buffers if the string is large in
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// that case the destruction of t does not de-allocate its buffer
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// but pulse might think it does if it fails to remember which
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// category t belongs to and follows impossibly control flow
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LikeFBString t = s;
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}
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void pass_to_copy_ok() {
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LikeFBString s;
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copy_fbstring(s);
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}
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