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829dbce | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 | #include "ctxstream.hpp"
#include <algorithm>
namespace ctxstream {
// Walk back from the target cut to the nearest record delimiter, so a segment
// never ends mid-row. A row split across two segments is counted twice or not
// at all, and both are silent corruption of the tally.
static std::size_t snap_to_boundary(const std::string& text, std::size_t target,
const ManifestOptions& opt) {
if (target >= text.size()) return text.size();
const std::size_t floor =
target > opt.boundary_slack ? target - opt.boundary_slack : 0;
const std::size_t hit = text.rfind(opt.record_delim, target);
if (hit != std::string::npos && hit >= floor) {
return hit + opt.record_delim.size();
}
// No delimiter within slack: the data is not row-shaped, cut where asked.
return target;
}
std::vector<Segment> plan(const std::string& text, const ManifestOptions& opt) {
std::vector<Segment> out;
if (text.empty() || opt.segment_chars == 0) return out;
std::size_t pos = 0;
int index = 0;
while (pos < text.size()) {
const std::size_t want = std::min(pos + opt.segment_chars, text.size());
const std::size_t end = snap_to_boundary(text, want, opt);
// snap_to_boundary can land at or before pos on pathological input
// (a single row longer than the segment); force progress.
const std::size_t stop = end > pos ? end : want;
Segment s;
s.index = index++;
s.overlap_prefix = std::min(pos, opt.overlap_chars);
s.offset = pos - s.overlap_prefix;
s.length = stop - s.offset;
out.push_back(s);
if (stop >= text.size()) break;
pos = stop;
}
return out;
}
std::string segment_text(const std::string& text, const Segment& s) {
if (s.offset >= text.size()) return {};
return text.substr(s.offset, std::min(s.length, text.size() - s.offset));
}
} // namespace ctxstream
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