silver-ymz commented on code in PR #3004:
URL:
https://github.com/apache/incubator-opendal/pull/3004#discussion_r1314456551
##########
bindings/cpp/src/opendal.cpp:
##########
@@ -85,6 +87,70 @@ std::vector<Entry> Operator::list(std::string_view path) {
return entries;
}
+ReaderStream Operator::reader(std::string_view path) {
+ return {operator_.value()->reader(RUST_STR(path))};
+}
+
+// Reader
+
+// Development Note:
+// Because rust side can't get current pointer info of c++, so we delay the
+// `consume` operation to the next `fill_buf`. Please pay attention to call
+// `consume` and update c++ pointers before each `seek` and `fill_buf`
+// operation.
+
+ffi::SeekDir to_rust_seek_dir(std::ios_base::seekdir dir);
+
+ReaderStreamBuf::pos_type
+ReaderStreamBuf::seekoff(ReaderStreamBuf::off_type off,
+ std::ios_base::seekdir dir,
+ std::ios_base::openmode which) {
+ if (!(which & std::ios_base::in)) {
+ return -1;
+ }
+
+ if (gptr() != nullptr) {
+ reader_->consume(gptr() - eback());
+ setg(gptr(), gptr(), egptr());
+ }
+
+ if (dir == std::ios_base::cur) {
+ off += gptr() - eback();
+ }
+
+ auto res = reader_->seek(off, to_rust_seek_dir(dir));
+
+ auto buffer = reader_->buffer();
+ auto gbeg = (char *)(buffer.data());
+ auto gcurr = gbeg;
+ auto gend = gbeg + buffer.size();
+ setg(gbeg, gcurr, gend);
+
+ return res;
+}
+
+ReaderStreamBuf::pos_type
+ReaderStreamBuf::seekpos(ReaderStreamBuf::pos_type pos,
+ std::ios_base::openmode which) {
+ return seekoff(pos, std::ios_base::beg, which);
+}
+
+ReaderStreamBuf::int_type ReaderStreamBuf::underflow() {
+ if (gptr() != nullptr) {
+ reader_->consume(gptr() - eback());
+ setg(gptr(), gptr(), egptr());
+ }
+ auto buffer = reader_->fill_buf();
+ auto gbeg = (char *)(buffer.data());
+ auto gcurr = gbeg;
+ auto gend = gbeg + buffer.size();
+ setg(gbeg, gcurr, gend);
+
+ return gcurr == gend ? traits_type::eof() : traits_type::to_int_type(*gcurr);
Review Comment:
> Maybe we polish this part by giving gbeg, gcurr and gend a more meaningful
name?
`gbeg`, `gcurr`, `gend` is the name used in cpp document of
[setg](https://en.cppreference.com/w/cpp/io/basic_streambuf/setg).
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