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transmission/libtransmission/variant-json.cc

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// This file Copyright © 2008-2023 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#include <algorithm>
#include <array>
#include <cctype>
#include <cerrno> /* EILSEQ, EINVAL */
#include <cmath> /* fabs() */
#include <cstddef> // std::byte
#include <cstdint> // uint16_t
#include <cstdlib>
#include <cstring>
#include <deque>
#include <iterator> // std::back_inserter
#include <string>
#include <string_view>
#include <utility>
#define UTF_CPP_CPLUSPLUS 201703L
#include <utf8.h>
#include <fmt/core.h>
#include <fmt/compile.h>
#include <jsonsl.h>
#define LIBTRANSMISSION_VARIANT_MODULE
#include "libtransmission/error.h"
#include "libtransmission/quark.h"
#include "libtransmission/tr-assert.h"
#include "libtransmission/tr-buffer.h"
#include "libtransmission/utils.h"
#include "libtransmission/variant.h"
using namespace std::literals;
namespace
{
namespace parse_helpers
{
/* arbitrary value... this is much deeper than our code goes */
auto constexpr MaxDepth = size_t{ 64 };
struct json_wrapper_data
{
bool has_content;
size_t size;
std::string_view key;
std::string keybuf;
std::string strbuf;
tr_error* error;
std::deque<tr_variant*> stack;
tr_variant* top;
bool inplace = false;
/* A very common pattern is for a container's children to be similar,
* e.g. they may all be objects with the same set of keys. So when
* a container is popped off the stack, remember its size to use as
* a preallocation heuristic for the next container at that depth. */
std::array<size_t, MaxDepth> preallocGuess;
};
tr_variant* get_node(struct jsonsl_st* jsn)
{
auto* data = static_cast<struct json_wrapper_data*>(jsn->data);
auto* parent = std::empty(data->stack) ? nullptr : data->stack.back();
tr_variant* node = nullptr;
if (parent == nullptr)
{
node = data->top;
}
else if (tr_variantIsList(parent))
{
node = tr_variantListAdd(parent);
}
else if (tr_variantIsDict(parent) && !std::empty(data->key))
{
node = tr_variantDictAdd(parent, tr_quark_new(data->key));
data->key = ""sv;
}
return node;
}
void error_handler(jsonsl_t jsn, jsonsl_error_t error, jsonsl_state_st* /*state*/, jsonsl_char_t const* buf)
{
auto* data = static_cast<struct json_wrapper_data*>(jsn->data);
tr_error_set(
&data->error,
EILSEQ,
fmt::format(
_("Couldn't parse JSON at position {position} '{text}': {error} ({error_code})"),
fmt::arg("position", jsn->pos),
fmt::arg("text", std::string_view{ buf, std::min(size_t{ 16U }, data->size - jsn->pos) }),
fmt::arg("error", jsonsl_strerror(error)),
fmt::arg("error_code", static_cast<int>(error))));
}
int error_callback(jsonsl_t jsn, jsonsl_error_t error, struct jsonsl_state_st* state, jsonsl_char_t* at)
{
error_handler(jsn, error, state, at);
return 0; /* bail */
}
void action_callback_PUSH(jsonsl_t jsn, jsonsl_action_t /*action*/, struct jsonsl_state_st* state, jsonsl_char_t const* /*buf*/)
{
auto* const data = static_cast<json_wrapper_data*>(jsn->data);
if ((state->type == JSONSL_T_LIST) || (state->type == JSONSL_T_OBJECT))
{
data->has_content = true;
tr_variant* node = get_node(jsn);
data->stack.push_back(node);
size_t const depth = std::size(data->stack);
size_t const n = depth < MaxDepth ? data->preallocGuess[depth] : 0;
if (state->type == JSONSL_T_LIST)
{
tr_variantInitList(node, n);
}
else
{
tr_variantInitDict(node, n);
}
}
}
/* like sscanf(in+2, "%4x", &val) but less slow */
[[nodiscard]] constexpr bool decode_hex_string(char const* in, std::uint16_t& setme)
{
TR_ASSERT(in != nullptr);
unsigned int val = 0;
char const* const end = in + 6;
TR_ASSERT(in[0] == '\\');
TR_ASSERT(in[1] == 'u');
in += 2;
do
{
val <<= 4;
if ('0' <= *in && *in <= '9')
{
val += *in - '0';
}
else if ('a' <= *in && *in <= 'f')
{
val += *in - 'a' + 10U;
}
else if ('A' <= *in && *in <= 'F')
{
val += *in - 'A' + 10U;
}
else
{
return false;
}
} while (++in != end);
setme = val;
return true;
}
template<typename Iter>
void decode_single_uchar(char const*& in, char const* const in_end, Iter& buf16_out_it)
{
static auto constexpr EscapedUcharLength = 6U;
if (in_end - in >= EscapedUcharLength && decode_hex_string(in, *buf16_out_it))
{
in += EscapedUcharLength;
++buf16_out_it;
}
}
[[nodiscard]] bool decode_escaped_uchar_sequence(char const*& in, char const* const in_end, std::string& buf)
{
auto buf16 = std::array<std::uint16_t, 2>{};
auto buf16_out_it = std::begin(buf16);
decode_single_uchar(in, in_end, buf16_out_it);
if (in[0] == '\\' && in[1] == 'u')
{
decode_single_uchar(in, in_end, buf16_out_it);
}
if (buf16_out_it == std::begin(buf16))
{
return false;
}
try
{
utf8::utf16to8(std::begin(buf16), buf16_out_it, std::back_inserter(buf));
}
catch (utf8::exception const&) // invalid codepoint
{
buf.push_back('?');
}
return true;
}
[[nodiscard]] std::string_view extract_escaped_string(char const* in, size_t in_len, std::string& buf)
{
char const* const in_end = in + in_len;
buf.clear();
while (in < in_end)
{
bool unescaped = false;
if (*in == '\\' && in_end - in >= 2)
{
switch (in[1])
{
case 'b':
buf.push_back('\b');
in += 2;
unescaped = true;
break;
case 'f':
buf.push_back('\f');
in += 2;
unescaped = true;
break;
case 'n':
buf.push_back('\n');
in += 2;
unescaped = true;
break;
case 'r':
buf.push_back('\r');
in += 2;
unescaped = true;
break;
case 't':
buf.push_back('\t');
in += 2;
unescaped = true;
break;
case '/':
buf.push_back('/');
in += 2;
unescaped = true;
break;
case '"':
buf.push_back('"');
in += 2;
unescaped = true;
break;
case '\\':
buf.push_back('\\');
in += 2;
unescaped = true;
break;
case 'u':
if (decode_escaped_uchar_sequence(in, in_end, buf))
{
unescaped = true;
break;
}
}
}
if (!unescaped)
{
buf.push_back(*in);
++in;
}
}
return buf;
}
[[nodiscard]] std::pair<std::string_view, bool> extract_string(jsonsl_t jsn, struct jsonsl_state_st* state, std::string& buf)
{
// figure out where the string is
char const* in_begin = jsn->base + state->pos_begin;
if (*in_begin == '"')
{
in_begin++;
}
char const* const in_end = jsn->base + state->pos_cur;
size_t const in_len = in_end - in_begin;
if (memchr(in_begin, '\\', in_len) == nullptr)
{
/* it's not escaped */
return std::make_pair(std::string_view{ in_begin, in_len }, true);
}
return std::make_pair(extract_escaped_string(in_begin, in_len, buf), false);
}
void action_callback_POP(jsonsl_t jsn, jsonsl_action_t /*action*/, struct jsonsl_state_st* state, jsonsl_char_t const* /*buf*/)
{
auto* data = static_cast<struct json_wrapper_data*>(jsn->data);
if (state->type == JSONSL_T_STRING)
{
auto const [str, inplace] = extract_string(jsn, state, data->strbuf);
if (inplace && data->inplace)
{
tr_variantInitStrView(get_node(jsn), str);
}
else
{
tr_variantInitStr(get_node(jsn), str);
}
data->has_content = true;
}
else if (state->type == JSONSL_T_HKEY)
{
data->has_content = true;
auto const [key, inplace] = extract_string(jsn, state, data->keybuf);
data->key = key;
}
else if (state->type == JSONSL_T_LIST || state->type == JSONSL_T_OBJECT)
{
auto const depth = std::size(data->stack);
auto const* const v = data->stack.back();
data->stack.pop_back();
if (depth < MaxDepth)
{
data->preallocGuess[depth] = v->val.l.count;
}
}
else if (state->type == JSONSL_T_SPECIAL)
{
if ((state->special_flags & JSONSL_SPECIALf_NUMNOINT) != 0)
{
auto sv = std::string_view{ jsn->base + state->pos_begin, jsn->pos - state->pos_begin };
tr_variantInitReal(get_node(jsn), tr_num_parse<double>(sv).value_or(0.0));
}
else if ((state->special_flags & JSONSL_SPECIALf_NUMERIC) != 0)
{
char const* begin = jsn->base + state->pos_begin;
data->has_content = true;
tr_variantInitInt(get_node(jsn), std::strtoll(begin, nullptr, 10));
}
else if ((state->special_flags & JSONSL_SPECIALf_BOOLEAN) != 0)
{
bool const b = (state->special_flags & JSONSL_SPECIALf_TRUE) != 0;
data->has_content = true;
tr_variantInitBool(get_node(jsn), b);
}
else if ((state->special_flags & JSONSL_SPECIALf_NULL) != 0)
{
data->has_content = true;
tr_variantInitQuark(get_node(jsn), TR_KEY_NONE);
}
}
}
} // namespace parse_helpers
} // namespace
std::optional<tr_variant> tr_variant_serde::parse_json(std::string_view input)
{
using namespace parse_helpers;
auto top = tr_variant{};
auto data = json_wrapper_data{};
data.error = nullptr;
data.size = std::size(input);
data.has_content = false;
data.key = ""sv;
data.inplace = parse_inplace_;
data.preallocGuess = {};
data.stack = {};
data.top = &top;
auto jsn = jsonsl_new(MaxDepth);
jsn->action_callback_PUSH = action_callback_PUSH;
jsn->action_callback_POP = action_callback_POP;
jsn->error_callback = error_callback;
jsn->data = &data;
jsonsl_enable_all_callbacks(jsn);
// parse it
jsonsl_feed(jsn, static_cast<jsonsl_char_t const*>(std::data(input)), std::size(input));
// EINVAL if there was no content
if (data.error == nullptr && !data.has_content)
{
tr_error_set(&data.error, EINVAL, "No content");
}
end_ = std::data(input) + jsn->pos;
if (data.error != nullptr)
{
tr_error_propagate(&error_, &data.error);
}
// cleanup
jsonsl_destroy(jsn);
if (error_ == nullptr)
{
return std::move(top);
}
return {};
}
// ---
namespace
{
namespace to_string_helpers
{
struct ParentState
{
bool is_map = false;
bool is_list = false;
size_t child_index;
size_t child_count;
};
struct JsonWalk
{
explicit JsonWalk(bool do_indent)
: doIndent{ do_indent }
{
}
std::deque<ParentState> parents;
libtransmission::StackBuffer<1024U * 8U, std::byte> out;
bool doIndent;
};
void jsonIndent(struct JsonWalk* data)
{
static auto buf = std::array<char, 1024>{};
if (buf.front() == '\0')
{
memset(std::data(buf), ' ', std::size(buf));
buf[0] = '\n';
}
if (data->doIndent)
{
data->out.add(std::data(buf), std::size(data->parents) * 4 + 1);
}
}
void jsonChildFunc(struct JsonWalk* data)
{
if (std::empty(data->parents))
{
return;
}
auto& parent_state = data->parents.back();
if (parent_state.is_map)
{
int const i = parent_state.child_index;
++parent_state.child_index;
if (i % 2 == 0)
{
data->out.add(data->doIndent ? ": "sv : ":"sv);
}
else
{
bool const is_last = parent_state.child_index == parent_state.child_count;
if (!is_last)
{
data->out.push_back(',');
jsonIndent(data);
}
}
}
else if (parent_state.is_list)
{
++parent_state.child_index;
if (bool const is_last = parent_state.child_index == parent_state.child_count; !is_last)
{
data->out.push_back(',');
jsonIndent(data);
}
}
}
void jsonPushParent(struct JsonWalk* data, tr_variant const& v)
{
auto const is_dict = tr_variantIsDict(&v);
auto const is_list = tr_variantIsList(&v);
auto const n_children = is_dict ? v.val.l.count * 2U : v.val.l.count;
data->parents.push_back({ is_dict, is_list, 0, n_children });
}
void jsonPopParent(struct JsonWalk* data)
{
data->parents.pop_back();
}
void jsonIntFunc(tr_variant const& /*var*/, int64_t const val, void* vdata)
{
auto buf = std::array<char, 64>{};
auto const* const out = fmt::format_to(std::data(buf), FMT_COMPILE("{:d}"), val);
auto* const data = static_cast<JsonWalk*>(vdata);
data->out.add(std::data(buf), static_cast<size_t>(out - std::data(buf)));
jsonChildFunc(data);
}
void jsonBoolFunc(tr_variant const& /*var*/, bool const val, void* vdata)
{
auto* data = static_cast<struct JsonWalk*>(vdata);
data->out.add(val ? "true"sv : "false"sv);
jsonChildFunc(data);
}
void jsonRealFunc(tr_variant const& /*var*/, double const val, void* vdata)
{
auto* const data = static_cast<struct JsonWalk*>(vdata);
auto const [buf, buflen] = data->out.reserve_space(64);
auto* walk = reinterpret_cast<char*>(buf);
auto const* const begin = walk;
if (fabs(val - (int)val) < 0.00001)
{
walk = fmt::format_to(walk, FMT_COMPILE("{:.0f}"), val);
}
else
{
walk = fmt::format_to(walk, FMT_COMPILE("{:.4f}"), val);
}
data->out.commit_space(walk - begin);
jsonChildFunc(data);
}
[[nodiscard]] char* write_escaped_char(char* buf, char const* const end, std::string_view& sv)
{
auto u16buf = std::array<std::uint16_t, 2>{};
auto const* const begin8 = std::data(sv);
auto const* const end8 = begin8 + std::size(sv);
auto const* walk8 = begin8;
utf8::next(walk8, end8);
auto const end16 = utf8::utf8to16(begin8, walk8, std::begin(u16buf));
for (auto it = std::cbegin(u16buf); it != end16; ++it)
{
buf = fmt::format_to_n(buf, end - buf - 1, FMT_COMPILE("\\u{:04x}"), *it).out;
}
sv.remove_prefix(walk8 - begin8 - 1);
return buf;
}
void jsonStringFunc(tr_variant const& /*var*/, std::string_view sv, void* vdata)
{
auto* const data = static_cast<struct JsonWalk*>(vdata);
auto& out = data->out;
auto const [buf, buflen] = out.reserve_space(std::size(sv) * 6 + 2);
auto* walk = reinterpret_cast<char*>(buf);
auto const* const begin = walk;
auto const* const end = begin + buflen;
*walk++ = '"';
for (; !std::empty(sv); sv.remove_prefix(1))
{
switch (sv.front())
{
case '\b':
*walk++ = '\\';
*walk++ = 'b';
break;
case '\f':
*walk++ = '\\';
*walk++ = 'f';
break;
case '\n':
*walk++ = '\\';
*walk++ = 'n';
break;
case '\r':
*walk++ = '\\';
*walk++ = 'r';
break;
case '\t':
*walk++ = '\\';
*walk++ = 't';
break;
case '"':
*walk++ = '\\';
*walk++ = '"';
break;
case '\\':
*walk++ = '\\';
*walk++ = '\\';
break;
default:
if (isprint((unsigned char)sv.front()) != 0)
{
*walk++ = sv.front();
}
else
{
try
{
walk = write_escaped_char(walk, end, sv);
}
catch (utf8::exception const&)
{
*walk++ = '?';
}
}
break;
}
}
*walk++ = '"';
TR_ASSERT(walk <= end);
out.commit_space(walk - begin);
jsonChildFunc(data);
}
void jsonDictBeginFunc(tr_variant const& var, void* vdata)
{
auto* const data = static_cast<struct JsonWalk*>(vdata);
jsonPushParent(data, var);
data->out.push_back('{');
if (var.val.l.count != 0U)
{
jsonIndent(data);
}
}
void jsonListBeginFunc(tr_variant const& var, void* vdata)
{
auto* const data = static_cast<struct JsonWalk*>(vdata);
jsonPushParent(data, var);
data->out.push_back('[');
if (var.val.l.count != 0U)
{
jsonIndent(data);
}
}
void jsonContainerEndFunc(tr_variant const& var, void* vdata)
{
auto* const data = static_cast<struct JsonWalk*>(vdata);
jsonPopParent(data);
jsonIndent(data);
if (tr_variantIsDict(&var))
{
data->out.push_back('}');
}
else /* list */
{
data->out.push_back(']');
}
jsonChildFunc(data);
}
} // namespace to_string_helpers
} // namespace
std::string tr_variant_serde::to_json_string(tr_variant const& var) const
{
using namespace to_string_helpers;
static auto constexpr Funcs = WalkFuncs{
jsonIntFunc, //
jsonBoolFunc, //
jsonRealFunc, //
jsonStringFunc, //
jsonDictBeginFunc, //
jsonListBeginFunc, //
jsonContainerEndFunc, //
};
auto data = JsonWalk{ !compact_ };
walk(var, Funcs, &data, true);
auto& buf = data.out;
if (!std::empty(buf))
{
buf.push_back('\n');
}
return buf.to_string();
}
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