117 lines
2.7 KiB
C++
117 lines
2.7 KiB
C++
// (C) 2018-2024 by Folkert van Heusden
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// Released under MIT license
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#include <cassert>
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#include <fcntl.h>
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#include <string.h>
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#include <unistd.h>
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#include "disk_backend_file.h"
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#include "gen.h"
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#include "log.h"
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disk_backend_file::disk_backend_file(const std::string & filename) :
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filename(filename)
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{
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}
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disk_backend_file::~disk_backend_file()
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{
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close(fd);
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}
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#if IS_POSIX
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json_t *disk_backend_file::serialize() const
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{
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json_t *j = json_object();
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json_object_set(j, "disk-backend-type", json_string("file"));
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json_object_set(j, "overlay", serialize_overlay());
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// TODO store checksum of backend
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json_object_set(j, "filename", json_string(filename.c_str()));
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return j;
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}
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disk_backend_file *disk_backend_file::deserialize(const json_t *const j)
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{
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// TODO verify checksum of backend
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return new disk_backend_file(json_string_value(json_object_get(j, "filename")));
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}
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#endif
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bool disk_backend_file::begin(const bool snapshots)
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{
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use_overlay = snapshots;
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fd = open(filename.c_str(), O_RDWR);
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if (fd == -1) {
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DOLOG(ll_error, true, "disk_backend_file: cannot open \"%s\": %s", filename.c_str(), strerror(errno));
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return false;
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}
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return true;
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}
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bool disk_backend_file::read(const off_t offset_in, const size_t n, uint8_t *const target, const size_t sector_size)
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{
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TRACE("disk_backend_file::read: read %zu bytes from offset %zu", n, offset_in);
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assert((offset_in % sector_size) == 0);
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assert((n % sector_size) == 0);
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for(off_t o=0; o<off_t(n); o+=sector_size) {
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off_t offset = offset_in + o;
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#if IS_POSIX
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auto o_rc = get_from_overlay(offset, sector_size);
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if (o_rc.has_value()) {
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memcpy(&target[o], o_rc.value().data(), sector_size);
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continue;
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}
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#endif
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#if defined(_WIN32) // hope for the best
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if (lseek(fd, offset, SEEK_SET) == -1)
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return false;
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if (::read(fd, target, n) != ssize_t(n))
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return false;
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#else
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ssize_t rc = pread(fd, target, n, offset);
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if (rc != ssize_t(n)) {
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DOLOG(warning, false, "disk_backend_file::read: read failure. expected %zu bytes, got %zd", n, rc);
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return false;
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}
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#endif
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}
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return true;
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}
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bool disk_backend_file::write(const off_t offset, const size_t n, const uint8_t *const from, const size_t sector_size)
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{
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TRACE("disk_backend_file::write: write %zu bytes to offset %zu", n, offset);
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if (store_mem_range_in_overlay(offset, n, from, sector_size))
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return true;
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#if defined(_WIN32) // hope for the best
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if (lseek(fd, offset, SEEK_SET) == -1)
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return false;
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return ::write(fd, from, n) == ssize_t(n);
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#else
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ssize_t rc = pwrite(fd, from, n, offset);
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if (rc != ssize_t(n)) {
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DOLOG(warning, false, "disk_backend_file::write: write failure. expected %zu bytes, got %zd", n, rc);
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return false;
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}
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return true;
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#endif
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}
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