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JSON parser: Improve by using exceptions to get exact error

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Also strip redundant "_Parser_" prefix from private methods.
This commit is contained in:
Stephan Aßmus 2014-08-30 23:24:40 +02:00
parent 7f9beaf1f8
commit ffd7c6110b
2 changed files with 102 additions and 44 deletions
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9
headers/private/shared/Json.h
View File

@ -22,10 +22,11 @@ public:
static status_t Parse(BMessage& message, BString& JSON);
private:
static BString _Parser_ParseString(BString& JSON, int32& pos);
static double _Parser_ParseNumber(BString& JSON, int32& pos);
static bool _Parser_ParseConstant(BString& JSON, int32& pos,
const char* constant);
static void _Parse(BMessage& message, BString& JSON);
static BString _ParseString(BString& JSON, int32& pos);
static double _ParseNumber(BString& JSON, int32& pos);
static bool _ParseConstant(BString& JSON, int32& pos,
const char* constant);
};
} // namespace BPrivate

137
src/kits/shared/Json.cpp
View File

@ -1,5 +1,6 @@
/*
* Copyright 2014, Augustin Cavalier (waddlesplash)
* Copyright 2014, Stephan Aßmus <superstippi@gmx.de>
* Distributed under the terms of the MIT License.
*/
@ -17,6 +18,46 @@
namespace BPrivate {
class ParseException {
public:
ParseException(int32 position, BString error)
:
fPosition(position),
fError(error),
fReturnCode(B_BAD_DATA)
{
}
ParseException(int32 position, status_t returnCode)
:
fPosition(position),
fError(""),
fReturnCode(returnCode)
{
}
void PrintToStream() const {
const char* error;
if (fError.Length() > 0)
error = fError.String();
else
error = strerror(fReturnCode);
printf("Parse error at %ld: %s\n", fPosition, error);
}
status_t ReturnCode() const
{
return fReturnCode;
}
private:
int32 fPosition;
BString fError;
status_t fReturnCode;
};
status_t
BJson::Parse(BMessage& message, const char* JSON)
{
@ -27,6 +68,23 @@ BJson::Parse(BMessage& message, const char* JSON)
status_t
BJson::Parse(BMessage& message, BString& JSON)
{
try {
_Parse(message, JSON);
return B_OK;
} catch (ParseException e) {
e.PrintToStream();
return e.ReturnCode();
}
return B_ERROR;
}
// #pragma mark - Private methods
void
BJson::_Parse(BMessage& message, BString& JSON)
{
BMessageBuilder builder(message);
int32 pos = 0;
@ -59,13 +117,13 @@ BJson::Parse(BMessage& message, BString& JSON)
break;
case '}':
if (hierarchy.EndsWith("{") && (hierarchy.Length() != 1)) {
if (hierarchy.EndsWith("{") && hierarchy.Length() != 1) {
hierarchy.Truncate(hierarchy.Length() - 1);
builder.PopObject();
} else if (hierarchy.Length() == 1)
return B_OK; // End of the JSON data
return; // End of the JSON data
else
return B_BAD_DATA; // Unmatched closebrace
throw ParseException(pos, "Unmatched closebrace }");
break;
@ -86,78 +144,80 @@ BJson::Parse(BMessage& message, BString& JSON)
if (hierarchy.EndsWith("[")) {
hierarchy.Truncate(hierarchy.Length() - 1);
builder.PopObject();
} else
return B_BAD_DATA; // Unmatched closebracket
} else {
BString error("Unmatched closebrace ] hierarchy: ");
error << hierarchy;
throw ParseException(pos, error);
}
break;
case 't':
{
if (builder.What() != JSON_TYPE_ARRAY && key.Length() == 0)
return B_BAD_DATA;
// 'true' cannot be a key, it can only be a value
if (builder.What() != JSON_TYPE_ARRAY && key.Length() == 0) {
throw ParseException(pos,
"'true' cannot be a key, it can only be a value");
}
if (_Parser_ParseConstant(JSON, pos, "true")) {
if (_ParseConstant(JSON, pos, "true")) {
if (builder.What() == JSON_TYPE_ARRAY)
key.SetToFormat("%" B_PRIu32, builder.CountNames());
builder.AddBool(key.String(), true);
key = "";
} else
return B_BAD_DATA;
// "t" out in the middle of nowhere!?
throw ParseException(pos, "Unexpected 't'");
break;
}
case 'f':
{
if (builder.What() != JSON_TYPE_ARRAY && key.Length() == 0)
return B_BAD_DATA;
// 'false' cannot be a key, it can only be a value
if (builder.What() != JSON_TYPE_ARRAY && key.Length() == 0) {
throw ParseException(pos,
"'false' cannot be a key, it can only be a value");
}
if (_Parser_ParseConstant(JSON, pos, "false")) {
if (_ParseConstant(JSON, pos, "false")) {
if (builder.What() == JSON_TYPE_ARRAY)
key.SetToFormat("%" B_PRIu32, builder.CountNames());
builder.AddBool(key.String(), false);
key = "";
} else
return B_BAD_DATA;
// "f" out in the middle of nowhere!?
throw ParseException(pos, "Unexpected 'f'");
break;
}
case 'n':
{
if (builder.What() != JSON_TYPE_ARRAY && key.Length() == 0)
return B_BAD_DATA;
// 'null' cannot be a key, it can only be a value
if (builder.What() != JSON_TYPE_ARRAY && key.Length() == 0) {
throw ParseException(pos,
"'null' cannot be a key, it can only be a value");
}
if (_Parser_ParseConstant(JSON, pos, "null")) {
if (_ParseConstant(JSON, pos, "null")) {
if (builder.What() == JSON_TYPE_ARRAY)
key.SetToFormat("%" B_PRIu32, builder.CountNames());
builder.AddPointer(key.String(), (void*)NULL);
key = "";
} else
return B_BAD_DATA;
// "n" out in the middle of nowhere!?
throw ParseException(pos, "Unexpected 'n'");
break;
}
case '"':
if (builder.What() != JSON_TYPE_ARRAY && key.Length() == 0)
key = _Parser_ParseString(JSON, pos);
key = _ParseString(JSON, pos);
else if (builder.What() != JSON_TYPE_ARRAY && key.Length() > 0) {
builder.AddString(key, _Parser_ParseString(JSON, pos));
builder.AddString(key, _ParseString(JSON, pos));
key = "";
} else if (builder.What() == JSON_TYPE_ARRAY) {
key << builder.CountNames();
builder.AddString(key, _Parser_ParseString(JSON, pos));
builder.AddString(key, _ParseString(JSON, pos));
key = "";
} else
return B_BAD_DATA;
// Pretty sure it's impossible to get here, but you never know
throw ParseException(pos, "Internal error at encountering \"");
break;
@ -174,14 +234,15 @@ BJson::Parse(BMessage& message, BString& JSON)
case '8':
case '9':
{
if (builder.What() != JSON_TYPE_ARRAY && key.Length() == 0)
return B_BAD_DATA;
// Numbers cannot be keys, they can only be values
if (builder.What() != JSON_TYPE_ARRAY && key.Length() == 0) {
throw ParseException(pos,
"Numbers cannot be keys, they can only be values");
}
if (builder.What() == JSON_TYPE_ARRAY)
key << builder.CountNames();
double number = _Parser_ParseNumber(JSON, pos);
double number = _ParseNumber(JSON, pos);
builder.AddDouble(key.String(), number);
key = "";
@ -197,16 +258,12 @@ BJson::Parse(BMessage& message, BString& JSON)
pos++;
}
// Reached the end of the BString without reaching the end of the document
return B_BAD_DATA;
throw ParseException(pos, "Unexpected end of document");
}
// #pragma mark - Private methods
BString
BJson::_Parser_ParseString(BString& JSON, int32& pos)
BJson::_ParseString(BString& JSON, int32& pos)
{
if (JSON[pos] != '"') // Verify we're at the start of a string.
return BString("");
@ -270,7 +327,7 @@ BJson::_Parser_ParseString(BString& JSON, int32& pos)
double
BJson::_Parser_ParseNumber(BString& JSON, int32& pos)
BJson::_ParseNumber(BString& JSON, int32& pos)
{
BString value;
@ -309,7 +366,7 @@ BJson::_Parser_ParseNumber(BString& JSON, int32& pos)
bool
BJson::_Parser_ParseConstant(BString& JSON, int32& pos, const char* constant)
BJson::_ParseConstant(BString& JSON, int32& pos, const char* constant)
{
BString value;
JSON.CopyInto(value, pos, strlen(constant));