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Add readahead to VariantParser
Adds a readahead buffer to VariantParser, to prevent large numbers of freads for single bytes, which is inefficient.
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parent
607964e973
commit
3d1640eb70
@ -35,36 +35,77 @@
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#include "core/os/keyboard.h"
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#include "core/string/string_buffer.h"
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CharType VariantParser::StreamFile::get_char() {
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return f->get_8();
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CharType VariantParser::Stream::get_char() {
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// is within buffer?
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if (readahead_pointer < readahead_filled) {
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return readahead_buffer[readahead_pointer++];
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}
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// attempt to readahead
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readahead_filled = _read_buffer(readahead_buffer, READAHEAD_SIZE);
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if (readahead_filled) {
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readahead_pointer = 0;
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} else {
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// EOF
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readahead_pointer = 1;
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eof = true;
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return 0;
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}
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return get_char();
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}
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uint32_t VariantParser::StreamFile::_read_buffer(CharType *p_buffer, uint32_t p_num_chars) {
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// The buffer is assumed to include at least one character (for null terminator)
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ERR_FAIL_COND_V(!p_num_chars, 0);
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uint8_t *temp = (uint8_t *)alloca(p_num_chars);
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uint64_t num_read = f->get_buffer(temp, p_num_chars);
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ERR_FAIL_COND_V(num_read == UINT64_MAX, 0);
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// translate to wchar
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for (uint32_t n = 0; n < num_read; n++) {
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p_buffer[n] = temp[n];
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}
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// could be less than p_num_chars, or zero
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return num_read;
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}
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bool VariantParser::StreamFile::is_utf8() const {
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return true;
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}
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bool VariantParser::StreamFile::is_eof() const {
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return f->eof_reached();
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}
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CharType VariantParser::StreamString::get_char() {
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if (pos > s.length()) {
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return 0;
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} else if (pos == s.length()) {
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// You need to try to read again when you have reached the end for EOF to be reported,
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// so this works the same as files (like StreamFile does)
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pos++;
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return 0;
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} else {
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return s[pos++];
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uint32_t VariantParser::StreamString::_read_buffer(CharType *p_buffer, uint32_t p_num_chars) {
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// The buffer is assumed to include at least one character (for null terminator)
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ERR_FAIL_COND_V(!p_num_chars, 0);
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int available = MAX(s.length() - pos, 0);
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if (available >= (int)p_num_chars) {
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const CharType *src = s.ptr();
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src += pos;
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memcpy(p_buffer, src, p_num_chars * sizeof(CharType));
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pos += p_num_chars;
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return p_num_chars;
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}
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// going to reach EOF
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if (available) {
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const CharType *src = s.ptr();
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src += pos;
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memcpy(p_buffer, src, available * sizeof(CharType));
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pos += available;
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}
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// add a zero
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p_buffer[available] = 0;
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return available;
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}
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bool VariantParser::StreamString::is_utf8() const {
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return false;
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}
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bool VariantParser::StreamString::is_eof() const {
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return pos > s.length();
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}
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/////////////////////////////////////////////////////////////////////////////////////////////////
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@ -37,35 +37,50 @@
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class VariantParser {
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public:
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struct Stream {
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virtual CharType get_char() = 0;
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virtual bool is_utf8() const = 0;
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virtual bool is_eof() const = 0;
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private:
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enum { READAHEAD_SIZE = 2048 };
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CharType readahead_buffer[READAHEAD_SIZE];
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uint32_t readahead_pointer = 0;
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uint32_t readahead_filled = 0;
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bool eof = false;
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protected:
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virtual uint32_t _read_buffer(CharType *p_buffer, uint32_t p_num_chars) = 0;
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public:
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CharType saved;
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CharType get_char();
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virtual bool is_utf8() const = 0;
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bool is_eof() const { return eof; }
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Stream() :
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saved(0) {}
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virtual ~Stream() {}
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};
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struct StreamFile : public Stream {
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protected:
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virtual uint32_t _read_buffer(CharType *p_buffer, uint32_t p_num_chars);
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public:
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FileAccess *f;
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virtual CharType get_char();
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virtual bool is_utf8() const;
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virtual bool is_eof() const;
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StreamFile() { f = nullptr; }
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};
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struct StreamString : public Stream {
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String s;
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private:
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int pos;
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virtual CharType get_char();
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virtual bool is_utf8() const;
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virtual bool is_eof() const;
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protected:
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virtual uint32_t _read_buffer(CharType *p_buffer, uint32_t p_num_chars);
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public:
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String s;
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virtual bool is_utf8() const;
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StreamString() { pos = 0; }
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};
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