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state machine
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@chadaustin
chadaustin committed Apr 29, 2017
1 parent 4a0cd70 commit 05b3ec8
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Showing 2 changed files with 132 additions and 80 deletions.
198 changes: 125 additions & 73 deletions include/sajson.h
View file
Expand Up @@ -41,10 +41,12 @@
#define SAJSON_LIKELY(x) __builtin_expect(!!(x), 1)
#define SAJSON_UNLIKELY(x) __builtin_expect(!!(x), 0)
#define SAJSON_ALWAYS_INLINE __attribute__((always_inline))
#define SAJSON_UNREACHABLE() __builtin_unreachable()
#else
#define SAJSON_LIKELY(x) x
#define SAJSON_UNLIKELY(x) x
#define SAJSON_ALWAYS_INLINE __forceinline
#define SAJSON_UNREACHABLE() assert(!"unreachable")
#endif

namespace sajson {
Expand Down Expand Up @@ -952,6 +954,14 @@ namespace sajson {
return error(p, "out of memory");
}

error_result unexpected_end() {
return error(0, "unexpected end of input");
}

error_result unexpected_end(char* p) {
return error(p, "unexpected end of input");
}

error_result error(char* p, const char* format, ...) {
if (!p) {
p = input_end;
Expand Down Expand Up @@ -996,17 +1006,17 @@ namespace sajson {
// p points to the character currently being parsed
char* p = input.get_data();

if (allocator.failed_to_initialize()) {
if (SAJSON_UNLIKELY(allocator.failed_to_initialize())) {
return oom(p);
}

auto stack = allocator.get_stack_head();
if (stack.has_allocation_error()) {
if (SAJSON_UNLIKELY(stack.has_allocation_error())) {
return oom(p);
}

p = skip_whitespace(p);
if (p == 0) {
if (SAJSON_UNLIKELY(!p)) {
return error(p, "missing root element");
}

Expand All @@ -1026,82 +1036,126 @@ namespace sajson {
return oom(p);
}

bool had_comma = false;
goto after_comma;

for (;;) {
p = skip_whitespace(p);
if (SAJSON_UNLIKELY(!p)) {
return error(p, "unexpected end of input");
}
// BEGIN STATE MACHINE

if (*p == (current_structure_type == TYPE_OBJECT ? '}' : ']')) {
goto check_pop;
}
if (SAJSON_UNLIKELY(*p != ',')) {
return error(p, "expected ,");
}
had_comma = true;
size_t pop_element; // used as an argument into the `pop` routine
goto structure_close_or_element;

if (0) { // purely for scoping

after_comma:
// ASSUMES: byte at p SHOULD be skipped
structure_close_or_element:
p = skip_whitespace(p + 1);
if (SAJSON_UNLIKELY(!p)) {
return error(p, "unexpected end of input 1");
return unexpected_end();
}
check_pop:
size_t pop_element; // used as an argument into the `pop` routine
if (TYPE_OBJECT == current_structure_type) {
if (*p == '}') {
if (had_comma) {
return error(p, "trailing commas not allowed");
}
++p;
size_t* base_ptr = stack.get_pointer_from_offset(current_base);
pop_element = *base_ptr;
if (!install_object(base_ptr + 1, stack.get_top())) {
return oom(p);
}
goto pop;
if (current_structure_type == TYPE_ARRAY) {
if (*p == ']') {
goto pop_array;
} else {
if (*p != '"') {
return error(p, "invalid object key");
}
size_t* out = stack.reserve(2);
if (stack.has_allocation_error()) {
return oom(p);
}
p = parse_string(p, out);
if (!p) {
return false;
}
p = skip_whitespace(p);
if (!p || *p != ':') {
return error(p, "expected :");
}
p = skip_whitespace(p + 1);
goto next_element;
}
} else {
assert(TYPE_ARRAY == current_structure_type);
assert(current_structure_type == TYPE_OBJECT);
if (*p == '}') {
goto pop_object;
} else {
goto object_key;
}
}
SAJSON_UNREACHABLE();

// ASSUMES: byte at p SHOULD NOT be skipped
structure_close_or_comma:
p = skip_whitespace(p);
if (SAJSON_UNLIKELY(!p)) {
return unexpected_end();
}

if (current_structure_type == TYPE_ARRAY) {
if (*p == ']') {
if (had_comma) {
return error(p, "trailing commas not allowed");
goto pop_array;
} else {
if (SAJSON_UNLIKELY(*p != ',')) {
return error(p, "expected ,");
}
++p;
size_t* base_ptr = stack.get_pointer_from_offset(current_base);
pop_element = *base_ptr;
if (!install_array(base_ptr + 1, stack.get_top())) {
return oom(p);
goto next_element;
}
} else {
assert(current_structure_type == TYPE_OBJECT);
if (*p == '}') {
goto pop_object;
} else {
if (SAJSON_UNLIKELY(*p != ',')) {
return error(p, "expected ,");
}
goto pop;
++p;
goto object_key;
}
}
SAJSON_UNREACHABLE();

// ASSUMES: *p == '}'
pop_object: {
++p;
size_t* base_ptr = stack.get_pointer_from_offset(current_base);
pop_element = *base_ptr;
if (!install_object(base_ptr + 1, stack.get_top())) {
return oom(p);
}
goto pop;
}

// ASSUMES: *p == ']'
pop_array: {
++p;
size_t* base_ptr = stack.get_pointer_from_offset(current_base);
pop_element = *base_ptr;
if (!install_array(base_ptr + 1, stack.get_top())) {
return oom(p);
}
goto pop;
}

// ASSUMES: byte at p SHOULD NOT be skipped
object_key: {
p = skip_whitespace(p);
if (SAJSON_UNLIKELY(!p)) {
return unexpected_end();
}
if (SAJSON_UNLIKELY(*p != '"')) {
return error(p, "missing object key");
}
size_t* out = stack.reserve(2);
if (stack.has_allocation_error()) {
return oom(p);
}
p = parse_string(p, out);
if (!p) {
return false;
}
p = skip_whitespace(p);
if (!p || *p != ':') {
return error(p, "expected :");
}
++p;
goto next_element;
}

// ASSUMES: byte at p SHOULD NOT be skipped
next_element:
p = skip_whitespace(p);
if (SAJSON_UNLIKELY(!p)) {
return unexpected_end();
}

type value_type_result;
switch (p ? *p : 0) {
switch (*p) {
type next_type;

case 0:
return error(p, "unexpected end of input");
return unexpected_end(p);
case 'n':
p = parse_null(p);
if (!p) {
Expand Down Expand Up @@ -1169,42 +1223,40 @@ namespace sajson {
return oom(p);
}
current_structure_type = next_type;
had_comma = false;
goto after_comma;
goto structure_close_or_element;
}

pop: {
size_t parent = get_element_value(pop_element);
if (parent == ROOT_MARKER) {
root_type = current_structure_type;
goto done;
p = skip_whitespace(p);
if (SAJSON_UNLIKELY(p)) {
return error(p, "expected end of input");
}
return true;
}
stack.reset(current_base);
current_base = parent;
value_type_result = current_structure_type;
current_structure_type = get_element_type(pop_element);
break;
}

case ',':
return error(p, "unexpected comma");
default:
return error(p, "expected value");
}

stack.push(make_element(value_type_result, allocator.get_write_offset()));
if (stack.has_allocation_error()) {
return oom(p);
}
had_comma = false;
}

done:
p = skip_whitespace(p);
if (0 == p) {
return true;
} else {
return error(p, "expected end of input");
goto structure_close_or_comma;
}

SAJSON_UNREACHABLE();
}

bool has_remaining_characters(char* p, ptrdiff_t remaining) {
Expand Down
14 changes: 7 additions & 7 deletions tests/test.cpp
View file
Expand Up @@ -29,8 +29,8 @@ inline bool success(const document& doc) {

#define ABSTRACT_TEST(name) \
static void name##internal(sajson::document (*parse)(const sajson::literal&)); \
TEST(single_allocation##name) { name##internal(&sajson::parse<sajson::single_allocation>); } \
TEST(dynamic_allocation##name) { name##internal(&sajson::parse<sajson::dynamic_allocation>); } \
TEST(single_allocation_##name) { name##internal(&sajson::parse<sajson::single_allocation>); } \
TEST(dynamic_allocation_##name) { name##internal(&sajson::parse<sajson::dynamic_allocation>); } \
static void name##internal(sajson::document (*parse)(const sajson::literal&))

ABSTRACT_TEST(empty_array) {
Expand Down Expand Up @@ -329,23 +329,23 @@ SUITE(commas) {
CHECK_EQUAL(false, document.is_valid());
CHECK_EQUAL(1u, document.get_error_line());
CHECK_EQUAL(2u, document.get_error_column());
CHECK_EQUAL("invalid object key", document.get_error_message());
CHECK_EQUAL("missing object key", document.get_error_message());
}

ABSTRACT_TEST(trailing_comma_array) {
const sajson::document& document = parse(literal("[1,2,]"));
CHECK_EQUAL(false, document.is_valid());
CHECK_EQUAL(1u, document.get_error_line());
CHECK_EQUAL(6u, document.get_error_column());
CHECK_EQUAL("trailing commas not allowed", document.get_error_message());
CHECK_EQUAL("expected value", document.get_error_message());
}

ABSTRACT_TEST(trailing_comma_object) {
const sajson::document& document = parse(literal("{\"key\": 0,}"));
CHECK_EQUAL(false, document.is_valid());
CHECK_EQUAL(1u, document.get_error_line());
CHECK_EQUAL(11u, document.get_error_column());
CHECK_EQUAL("trailing commas not allowed", document.get_error_message());
CHECK_EQUAL("missing object key", document.get_error_message());
}
}

Expand Down Expand Up @@ -622,7 +622,7 @@ SUITE(errors) {
CHECK_EQUAL(false, document.is_valid());
CHECK_EQUAL(1u, document.get_error_line());
CHECK_EQUAL(2u, document.get_error_column());
CHECK_EQUAL("invalid object key", document.get_error_message());
CHECK_EQUAL("missing object key", document.get_error_message());
}

ABSTRACT_TEST(objects_must_have_keys) {
Expand Down Expand Up @@ -678,7 +678,7 @@ SUITE(errors) {
CHECK_EQUAL(false, document.is_valid());
CHECK_EQUAL(1u, document.get_error_line());
CHECK_EQUAL(2u, document.get_error_column());
CHECK_EQUAL("invalid object key", document.get_error_message());
CHECK_EQUAL("missing object key", document.get_error_message());
}

#define CHECK_PARSE_ERROR(text, error_message) \
Expand Down

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