123 lines
4.2 KiB
C++
123 lines
4.2 KiB
C++
/* @file log_streambuf.hpp */
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#pragma once
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#include <iostream>
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#include <vector>
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#include <cstring> // e.g. for std::memcpy()
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#include <cstdint>
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#include <cassert>
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namespace xo {
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/* recycling buffer for logging.
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* write to self-extending storage array;
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*/
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template <typename CharT, typename Traits>
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class log_streambuf : public std::streambuf {
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public:
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log_streambuf(std::uint32_t buf_z) {
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this->buf_v_.resize(buf_z);
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this->reset_stream();
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} /*ctor*/
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std::streamsize capacity() const { return this->buf_v_.size(); }
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char const * lo() const { return this->pbase(); }
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char const * hi() const { return this->lo() + this->capacity(); }
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std::uint32_t pos() const { return this->pptr() - this->pbase(); }
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void reset_stream() {
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char * p_lo = &(this->buf_v_[0]);
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char * p_hi = p_lo + this->capacity();
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/* tells parent our buffer extent */
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this->setp(p_lo, p_hi);
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} /*reset_stream*/
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protected:
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virtual std::streamsize
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xsputn(char const * s, std::streamsize n) override {
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/* s must be an address in [this->lo() .. this->lo() + capacity()] */
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assert(this->hi() >= this->pptr());
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#ifdef NOT_USING_DEBUG
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std::cout << "xsputn: pbase=" << (void *)(this->pbase())
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<< ", pptr=" << (void*)(this->pptr())
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<< "(+" << (this->pptr() - this->lo()) << ")"
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<< ", n=" << n << " -> (+" << (this->pptr() + n - this->lo()) << ")"
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<< ", buf_v.size=" << this->buf_v_.size()
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<< std::endl;
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#endif
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//std::cout << "xsputn: s=" << quoted(string_view(s, n)) << ", n=" << n << std::endl;
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if (this->pptr() + n > this->hi()) {
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n = this->hi() - this->pptr();
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std::memcpy(this->pptr(), s, n);
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} else {
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std::memcpy(this->pptr(), s, n);
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}
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this->pbump(n);
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return n;
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} /*xsputn*/
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virtual int_type
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overflow(int_type new_ch) override
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{
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char * old_pptr = this->pptr();
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std::streamsize old_n = old_pptr - this->pbase();
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assert(old_n <= static_cast<std::streamsize>(this->buf_v_.size()));
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std::size_t new_z = 2 * this->buf_v_.size();
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this->buf_v_.resize(new_z);
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this->buf_v_[old_n] = new_ch;
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/* 'buffered range' will now be .buf_v[old_n .. new_z] */
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char * p_base = &(this->buf_v_[0]);
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//char * p_lo = &(this->buf_v_[old_n+1]);
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char * p_hi = p_base + this->buf_v_.capacity();
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this->setp(p_base, p_hi);
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this->pbump(old_n + 1);
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return new_ch;
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} /*overflow*/
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/* off. offset, relative to starting point dir.
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* dir.
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* which. in|out|both
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*/
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virtual pos_type seekoff(off_type off,
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std::ios_base::seekdir dir,
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std::ios_base::openmode which) override {
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//std::cout << "seekoff: off=" << off << ", dir=" << dir << ", which=" << which << std::endl;
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// Only output stream is supported
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if (which != std::ios_base::out)
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throw std::runtime_error("log_streambuf: only output mode supported");
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if (dir == std::ios_base::cur) {
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this->pbump(off);
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} else if (dir == std::ios_base::end) {
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/* .setp(): using for side effect: sets .pptr to .pbase */
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this->setp(this->pbase(), this->epptr());
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this->pbump(off);
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} else if (dir == std::ios_base::beg) {
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/* .setp(): using for side effect: sets .pptr to .pbase */
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this->setp(this->pbase(), this->epptr());
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this->pbump(this->capacity() + off);
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}
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return this->pptr() - this->pbase();
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} /*seekoff*/
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private:
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/* buffered output stored here */
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std::vector<char> buf_v_;
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}; /*log_streambuf*/
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} /*namespace xo*/
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/* end log_streambuf.hpp */
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