capnproto

readiness-io.c++ (5022B)

---

 // Copyright (c) 2016 Sandstorm Development Group, Inc. and contributors
 // Licensed under the MIT License:
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
 // in the Software without restriction, including without limitation the rights
 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 // copies of the Software, and to permit persons to whom the Software is
 // furnished to do so, subject to the following conditions:
 //
 // The above copyright notice and this permission notice shall be included in
 // all copies or substantial portions of the Software.
 //
 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
 #include "readiness-io.h"
 
 namespace kj {
 
 static size_t copyInto(kj::ArrayPtr<byte> dst, kj::ArrayPtr<const byte>& src) {
   size_t n = kj::min(dst.size(), src.size());
   memcpy(dst.begin(), src.begin(), n);
   src = src.slice(n, src.size());
   return n;
 }
 
 // =======================================================================================
 
 ReadyInputStreamWrapper::ReadyInputStreamWrapper(AsyncInputStream& input): input(input) {}
 ReadyInputStreamWrapper::~ReadyInputStreamWrapper() noexcept(false) {}
 
 kj::Maybe<size_t> ReadyInputStreamWrapper::read(kj::ArrayPtr<byte> dst) {
   if (eof || dst.size() == 0) return size_t(0);
 
   if (content.size() == 0) {
     // No data available. Try to read more.
     if (!isPumping) {
       isPumping = true;
       pumpTask = kj::evalNow([&]() {
         return input.tryRead(buffer, 1, sizeof(buffer)).then([this](size_t n) {
           if (n == 0) {
             eof = true;
           } else {
             content = kj::arrayPtr(buffer, n);
           }
           isPumping = false;
         });
       }).fork();
     }
 
     return nullptr;
   }
 
   return copyInto(dst, content);
 }
 
 kj::Promise<void> ReadyInputStreamWrapper::whenReady() {
   return pumpTask.addBranch();
 }
 
 // =======================================================================================
 
 ReadyOutputStreamWrapper::ReadyOutputStreamWrapper(AsyncOutputStream& output): output(output) {}
 ReadyOutputStreamWrapper::~ReadyOutputStreamWrapper() noexcept(false) {}
 
 kj::Maybe<size_t> ReadyOutputStreamWrapper::write(kj::ArrayPtr<const byte> data) {
   if (data.size() == 0) return size_t(0);
 
   if (filled == sizeof(buffer)) {
     // No space.
     return nullptr;
   }
 
   uint end = start + filled;
   size_t result = 0;
   if (end < sizeof(buffer)) {
     // The filled part of the buffer is somewhere in the middle.
 
     // Copy into space after filled space.
     result += copyInto(kj::arrayPtr(buffer + end, buffer + sizeof(buffer)), data);
 
     // Copy into space before filled space.
     result += copyInto(kj::arrayPtr(buffer, buffer + start), data);
   } else {
     // Fill currently loops, so we only have one segment of empty space to copy into.
 
     // Copy into the space between the fill's end and the fill's start.
     result += copyInto(kj::arrayPtr(buffer + end % sizeof(buffer), buffer + start), data);
   }
 
   filled += result;
 
   if (!isPumping && (!corked || filled == sizeof(buffer))) {
     isPumping = true;
     pumpTask = kj::evalNow([&]() {
       return pump();
     }).fork();
   }
 
   return result;
 }
 
 kj::Promise<void> ReadyOutputStreamWrapper::whenReady() {
   return pumpTask.addBranch();
 }
 
 ReadyOutputStreamWrapper::Cork ReadyOutputStreamWrapper::cork() {
   corked = true;
   return Cork(*this);
 }
 
 void ReadyOutputStreamWrapper::uncork() {
   corked = false;
   if (!isPumping && filled > 0) {
     isPumping = true;
     pumpTask = kj::evalNow([&]() {
       return pump();
     }).fork();
   }
 }
 
 kj::Promise<void> ReadyOutputStreamWrapper::pump() {
   uint oldFilled = filled;
   uint end = start + filled;
 
   kj::Promise<void> promise = nullptr;
   if (end <= sizeof(buffer)) {
     promise = output.write(buffer + start, filled);
   } else {
     end = end % sizeof(buffer);
     segments[0] = kj::arrayPtr(buffer + start, buffer + sizeof(buffer));
     segments[1] = kj::arrayPtr(buffer, buffer + end);
     promise = output.write(segments);
   }
 
   return promise.then([this,oldFilled,end]() -> kj::Promise<void> {
     filled -= oldFilled;
     start = end;
 
     if (filled > 0) {
       return pump();
     } else {
       isPumping = false;
       // As a small optimization, reset to the start of the buffer when it's empty so we can provide
       // the underlying layer just one contiguous chunk of memory instead of two when possible.
       start = 0;
       return kj::READY_NOW;
     }
   });
 }
 
 }  // namespace kj