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#include "io.hh"
#include "unique_fd.hh"
#include <algorithm>
#include <cerrno>
#include <cstdio>
#include <cstring>
#include <expected>
#include <fcntl.h>
#include <limits>
#include <memory>
#include <optional>
#include <string>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <utility>
namespace io {
namespace {
class BasicReader : public Reader {
public:
explicit BasicReader(unique_fd fd) : fd_(std::move(fd)) {}
[[nodiscard]]
std::expected<size_t, ReadError> read(void* dst, size_t max) override {
ssize_t ret = ::read(
fd_.get(), dst,
std::min(static_cast<size_t>(std::numeric_limits<ssize_t>::max()),
max));
if (ret < 0) {
switch (errno) {
case EINTR:
return read(dst, max);
default:
return std::unexpected(ReadError::Error);
}
} else if (ret == 0 && max > 0) {
return std::unexpected(ReadError::Eof);
}
offset_ += ret;
return ret;
}
[[nodiscard]]
std::expected<size_t, ReadError> skip(size_t max) override {
off_t ret;
if (sizeof(size_t) > sizeof(off_t)) {
ret = lseek(
fd_.get(),
// NOLINTNEXTLINE(bugprone-narrowing-conversions)
std::min(static_cast<size_t>(std::numeric_limits<off_t>::max()), max),
SEEK_CUR);
} else {
ret = lseek(fd_.get(), static_cast<off_t>(max), SEEK_CUR);
}
if (ret < 0) {
return std::unexpected(ReadError::Error);
}
// Don't want skip to go past (cached) file end.
if (!size_.has_value() || ret >= size_.value()) {
// When going past end, double check that it still is the end.
off_t ret2 = lseek(fd_.get(), 0, SEEK_END);
if (ret2 < 0) {
// We're screwed, but try to go back to original position and then
// return error.
size_.reset();
lseek(fd_.get(), offset_, SEEK_SET);
return std::unexpected(ReadError::Error);
}
size_ = ret2;
if (ret >= ret2) {
auto distance = ret2 - offset_;
offset_ = ret2;
if (distance == 0 && max > 0)
return std::unexpected(ReadError::Eof);
return distance;
}
// Seek back to where we should be
if (lseek(fd_.get(), ret, SEEK_SET) < 0) {
return std::unexpected(ReadError::Error);
}
}
auto distance = ret - offset_;
offset_ = ret;
return distance;
}
private:
unique_fd fd_;
off_t offset_{0};
std::optional<off_t> size_;
};
class MemoryReader : public Reader {
public:
MemoryReader(void* ptr, size_t size) : ptr_(ptr), size_(size) {}
[[nodiscard]]
std::expected<size_t, ReadError> read(void* dst, size_t max) override {
size_t avail = size_ - offset_;
if (avail == 0 && max > 0)
return std::unexpected(io::ReadError::Eof);
size_t ret = std::min(max, avail);
memcpy(dst, reinterpret_cast<char*>(ptr_) + offset_, ret);
offset_ += ret;
return ret;
}
[[nodiscard]]
std::expected<size_t, ReadError> skip(size_t max) override {
size_t avail = size_ - offset_;
size_t ret = std::min(max, avail);
offset_ += ret;
return ret;
}
protected:
void* ptr_;
size_t const size_;
private:
size_t offset_{0};
};
class MmapReader : public MemoryReader {
public:
MmapReader(unique_fd fd, void* ptr, size_t size)
: MemoryReader(ptr, size), fd_(std::move(fd)) {}
~MmapReader() override { munmap(ptr_, size_); }
private:
unique_fd fd_;
};
class StringReader : public MemoryReader {
public:
explicit StringReader(std::string data)
: MemoryReader(nullptr, data.size()), data_(std::move(data)) {
ptr_ = data_.data();
}
private:
std::string data_;
};
} // namespace
std::expected<size_t, ReadError> Reader::repeat_read(void* dst, size_t max) {
auto ret = read(dst, max);
if (!ret.has_value() || ret.value() == max)
return ret;
char* d = reinterpret_cast<char*>(dst);
size_t offset = ret.value();
while (true) {
ret = read(d + offset, max - offset);
if (!ret.has_value())
break;
offset += ret.value();
if (offset == max)
break;
}
return offset;
}
std::expected<size_t, ReadError> Reader::repeat_skip(size_t max) {
auto ret = skip(max);
if (!ret.has_value() || ret.value() == max)
return ret;
size_t offset = ret.value();
while (true) {
ret = skip(max - offset);
if (!ret.has_value())
break;
offset += ret.value();
if (offset == max)
break;
}
return offset;
}
std::expected<std::unique_ptr<Reader>, OpenError> open(
const std::string& file_path) {
return openat(AT_FDCWD, file_path);
}
std::expected<std::unique_ptr<Reader>, OpenError> openat(
int dirfd, const std::string& file_path) {
unique_fd fd(::openat(dirfd, file_path.c_str(), O_RDONLY));
if (fd) {
struct stat buf;
if (fstat(fd.get(), &buf) == 0) {
if (std::cmp_less_equal(buf.st_size,
std::numeric_limits<size_t>::max())) {
auto size = static_cast<size_t>(buf.st_size);
void* ptr = mmap(nullptr, size, PROT_READ, MAP_PRIVATE, fd.get(), 0);
if (ptr != MAP_FAILED) {
return std::make_unique<MmapReader>(std::move(fd), ptr, size);
}
}
}
return std::make_unique<BasicReader>(std::move(fd));
}
OpenError err;
switch (errno) {
case EINTR:
return openat(dirfd, file_path);
case EACCES:
err = OpenError::NoAccess;
break;
case ENOENT:
err = OpenError::NoSuchFile;
break;
default:
err = OpenError::Error;
break;
}
return std::unexpected(err);
}
std::unique_ptr<Reader> memory(std::string data) {
return std::make_unique<StringReader>(std::move(data));
}
} // namespace io
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