190 lines
6.6 KiB
C++
190 lines
6.6 KiB
C++
/* @file log_streambuf.hpp */
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#pragma once
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#include "print/quoted_char.hpp"
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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 and pretty-printing
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* - write to self-extending storage array
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* - track position relative to start of line
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**/
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template <typename CharT, typename Traits = std::char_traits<CharT>>
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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, bool debug_flag = false) : debug_flag_{debug_flag} {
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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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/** number of characters since start of line (last \n or \r) **/
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std::uint32_t lpos() const { return pos() - solpos_; }
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bool debug_flag() const { return debug_flag_; }
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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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this->solpos_ = 0;
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} /*reset_stream*/
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void rewind_to(std::uint32_t p) {
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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(p);
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}
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protected:
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/** expand buffer storage (by 2x), preserve current contents **/
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void
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expand_to(std::size_t new_z) {
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char * old_pptr = pptr();
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std::streamsize old_n = old_pptr - pbase();
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assert(old_n <= static_cast<std::streamsize>(buf_v_.size()));
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assert(new_z > buf_v_.capacity());
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this->buf_v_.resize(new_z);
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char * p_base = &(this->buf_v_[0]);
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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);
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} /*expand*/
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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(hi() >= pptr());
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if (pptr() + n > hi()) {
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this->expand_to(std::max(2 * this->buf_v_.capacity(), std::size_t(this->pos() + n + 1)));
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}
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if (debug_flag_) {
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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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}
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std::streamsize ncopied = 0;
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if (this->pptr() + n > this->hi()) {
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ncopied = this->hi() - this->pptr();
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} else {
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ncopied = n;
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}
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if (debug_flag_) {
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std::cout << "xsputn: copying ncopied=" << ncopied << " (/n=" << n << ") bytes into range [lo,hi)"
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<< ", lo=" << (void*)this->pptr()
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<< ", hi=" << (void*)(this->pptr() + n)
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<< std::endl;
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}
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std::memcpy(this->pptr(), s, ncopied);
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/* scan range [pptr, pptr+n] backwards, to account for newline (if any) */
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for (char const * p_lo = this->pptr(), * p_hi = p_lo + n - 1, * p = p_hi; p >= p_lo; --p) {
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if (*p == '\n' || *p == '\r') {
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this->solpos_ = (p+1 - this->pbase());
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break;
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}
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}
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this->pbump(ncopied);
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return ncopied;
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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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if (debug_flag_) {
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std::cout << "overflow: new_ch=" << quoted_char(new_ch) << std::endl;
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}
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this->expand_to(2 * buf_v_.size());
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this->buf_v_[old_n] = new_ch;
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this->pbump(1);
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if ((new_ch == static_cast<int_type>('\n')) || (new_ch == static_cast<int_type>('\r')))
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this->solpos_ = this->pos();
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if (new_ch == Traits::eof()) {
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/* reminder: returning eof sets badbit on ostream */
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return Traits::not_eof(new_ch);
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} else {
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return new_ch;
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}
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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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* Note that off=0,dir=cur,which=out reads offset
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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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/** position (relative to pbase) one character after last \n or \r.
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* Use to drive @ref lpos
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**/
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std::size_t solpos_ = 0;
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/** buffered output stored here **/
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std::vector<char> buf_v_;
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/** true to debug log_streambuf itself **/
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bool debug_flag_ = false;
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}; /*log_streambuf*/
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} /*namespace xo*/
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/* end log_streambuf.hpp */
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