Quellcode-Bibliothek

^© Kompilation durch diese Firma

[Weder Korrektheit noch Funktionsfähigkeit der Software werden zugesichert.]

Datei: json.cpp Sprache: C

/*
* Copyright (c) 2015, 2022, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/

/*
* This is not really json in the state it is now.
* Some differences:
* - Double quotes around the key in an object is not enforced.
*     i.e you can write: { foo : "bar" } instead of { "foo" : "bar" }.
* - Comments are allowed.
* - The last element in an object or array can have an ending comma.
*/

#include "precompiled.hpp"
#include "utilities/json.hpp"
#include "utilities/ostream.hpp"
#include <math.h>

const char* strchrnul_(const char *s, int c) {
  const char* tmp = strchr(s, c);
  return tmp == NULL ? s + strlen(s) : tmp;
}

JSON::JSON(const char* text, bool silent, outputStream* st)
: _st(st), start(text), pos(text), mark(text),
  level(0), line(1), column(0), silent(silent), _valid(true)
{
}

void JSON::parse() {
  assert(start != NULL, "Need something to parse");
  if (start == NULL) {
    _valid = false;
    error(INTERNAL_ERROR, "JSON parser was called with a string that was NULL.");
  } else {
    _valid = parse_json_value();
  }
}

bool JSON::valid() {
  return _valid;
}

bool JSON::parse_json_value() {
  int c;

  c = skip_to_token();
  if (c == -1) {
    return false;
  }

  // Must start with object or array
  if (level == 0) {

    switch (c) {
    case '{':
      if (parse_json_object() == false) {
        return false;
      }
      c = skip_to_token();
      if (c > 0) {
        mark_pos();
        error(SYNTAX_ERROR, "Only one top level object/array is allowed.");
        return false;
      } else if (c < 0) {
        return false;
      }
      return true;

    case '[':
      if (parse_json_array() == false) {
        return false;
      }
      c = skip_to_token();
      if (c > 0) {
        mark_pos();
        error(SYNTAX_ERROR, "Only one top level object/array is allowed.");
        return false;
      } else if (c < 0) {
        return false;
      }
      return true;

    case 0:
      error(SYNTAX_ERROR, "EOS was encountered before any json declarations");
      return false;

    default:
      error(SYNTAX_ERROR, "Json must start with an object or an array.");
      return false;
    }
  } else { // level > 0
    switch (c) {
    case '{':
      return parse_json_object();

    case '[':
      return parse_json_array();

    case '"':
      return parse_json_string();

    case '-': case '0':
    case '1': case '2': case '3':
    case '4': case '5': case '6':
    case '7': case '8': case '9':
      return parse_json_number();

    case 't':
      return parse_json_symbol("true", JSON_TRUE);

    case 'f':
      return parse_json_symbol("false", JSON_FALSE);

    case 'n':
      return parse_json_symbol("null", JSON_NULL);

    case 0:
      error(SYNTAX_ERROR, "EOS was encountered when expecting a json value.");
      return false;

    default:
      error(SYNTAX_ERROR, "Could not parse as a json value (did you forget to quote your strings?).");
      return false;
    }
  }
}

// Should only be called when we actually have the start of an object
// Otherwise it is an internal error
bool JSON::parse_json_object() {
  NOT_PRODUCT(const char* prev_pos);
  int c;

  mark_pos();
  // Check that we are not called in error
  if (expect_any("{", "object start", INTERNAL_ERROR) <= 0) {
    return false;
  }

  if (!callback(JSON_OBJECT_BEGIN, NULL, level++)) {
    return false;
  }

  for (;;) {
    mark_pos();
    c = skip_to_token();
    if (c == 0) {
      error(SYNTAX_ERROR, "EOS when expecting an object key or object end");
      return false;
    } else if (c < 0) {
      return false;
    } else if (c == '}') {
      // We got here from either empty object "{}" or ending comma "{a:1,}"
      next();
      break;
    }

    NOT_PRODUCT(prev_pos = pos);
    if (parse_json_key() == false) {
      return false;
    }
    assert(pos > prev_pos, "parsing stalled");

    skip_to_token();
    mark_pos();
    if (expect_any(":", "object key-value separator") <= 0) {
      return false;
    }

    skip_to_token();
    mark_pos();
    NOT_PRODUCT(prev_pos = pos);
    if (parse_json_value() == false) {
      return false;
    }
    assert(pos > prev_pos, "parsing stalled");

    c = skip_to_token();
    mark_pos();
    if (expect_any(",}", "value separator or object end") <= 0) {
      return false;
    }
    if (c == '}') {
      break;
    }
  }

  assert(c == '}', "array parsing ended without object end token ('}')");
  return callback(JSON_OBJECT_END, NULL, --level);
}

// Should only be called when we actually have the start of an array
// Otherwise it is an internal error
bool JSON::parse_json_array() {
  NOT_PRODUCT(const char* prev_pos);
  int c;

  mark_pos();
  // Check that we are not called in error
  if (expect_any("[", "array start character", INTERNAL_ERROR) <= 0) {
    return false;
  }

  if (!callback(JSON_ARRAY_BEGIN, NULL, level++)) {
    return false;
  }

  for (;;) {
    mark_pos();
    c = skip_to_token();
    if (c == 0) {
      error(SYNTAX_ERROR, "EOS when expecting a json value or array end");
      return false;
    } else if (c < 0) {
      return false;
    } else if (c == ']') {
      // We got here from either empty array "[]" or ending comma "[1,]"
      next();
      break;
    }

    mark_pos();
    NOT_PRODUCT(prev_pos = pos);
    if (parse_json_value() == false) {
      return false;
    }
    assert(pos > prev_pos, "parsing stalled");

    c = skip_to_token();
    mark_pos();
    if (expect_any(",]", "value separator or array end") <= 0) {
      return false;
    }
    if (c == ']') {
      break;
    }
  }

  assert(c == ']', "array parsing ended without array end token (']')");
  return callback(JSON_ARRAY_END, NULL, --level);
}

bool JSON::parse_json_string(bool key) {
  const char* end;
  JSON_VAL v;

  mark_pos();
  if (expect_any("\"", "string start character", INTERNAL_ERROR) <= 0) {
    return false;
  }

  end = strchr(pos, '"'); // TODO: escapes
  if (end == NULL) {
    error(SYNTAX_ERROR, "String started here never ended. Expected \'\"\' before EOS.");
    return false;
  }

  v.str.start = pos;
  v.str.length = end - pos;
  skip(end - pos);

  if (expect_any("\"", "string end character", INTERNAL_ERROR) <= 0) {
    return false;
  }

  if (key == true) {
    return callback(JSON_KEY, &v, level);
  } else {
    return callback(JSON_STRING, &v, level);
  }
}

// TODO: hotspot equivalents?
static bool is_alpha(u_char c) {
  return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
}
static bool is_numeric(u_char c) {
  return (c >= '0' && c <= '9');
}
static bool is_alnum(u_char c) {
  return is_alpha(c) || is_numeric(c);
}
static bool is_word(u_char c) {
  return c == '_' || is_alnum(c);
}

// Allow object keys to be without quotation,
// but then restrict to ([a-zA-Z0-9_])+
bool JSON::parse_json_key() {
  const char* begin;
  JSON_VAL v;
  u_char c;

  mark_pos();
  c = peek();
  if (c == '"') {
    return parse_json_string(true);
  }

  begin = pos;
  c = peek();
  if (c == 0) {
    error(SYNTAX_ERROR, "Got EOS when expecting an object key.");
    return false;
  } else if (is_word(c) == false) {
    error(SYNTAX_ERROR, "Expected an object key, which can be a double-quoted (\") string or a simple string (only alphanumeric characters and underscore, separated by whitespace) that doesn't need to be quoted.");
    return false;
  }

  for (;;) {
    c = peek();
    // Allow the key to be delimited by control characters and the object key-value separator ':'
    if (c <= ' ' || c == ':') {
      break;
    } else if (is_word(c) == false) {
      error(SYNTAX_ERROR, "Object key need to be quoted, or consist entirely of alphanumeric characters and underscores.");
      return false;
    }
    next();
  }

  v.str.start = begin;
  v.str.length = pos - begin;
  return callback(JSON_KEY, &v, level);
}

bool JSON::parse_json_number() {
  double double_value;
  int tokens, read;
  JSON_VAL v;

  mark_pos();

  // Parsing number - for simplicity ints are limited to 2**53
  // sscanf as a double and check if part is 0.
  tokens = sscanf(pos, "%lf%n", &double_value, &read);
  assert(tokens <= 1, "scanf implementation that counts as a token, parsing json numbers will always fail");
  if (tokens == 1) {
    assert(read > 0, "sanity");

    if (floor(double_value) == double_value) {
      // No exponent - treat as an int
      v.int_value = (int)double_value;
      if (!callback(JSON_NUMBER_INT, &v, level)) {
        return false;
      }
    } else {
      v.double_value = double_value;
      if (!callback(JSON_NUMBER_FLOAT, &v, level)) {
        return false;
      }
    }
    skip(read);
    return true;
  }

  error(SYNTAX_ERROR, "Couldn't parse json number (note that exponents are not supported).");
  return false;
}

bool JSON::parse_json_symbol(const char* name, JSON_TYPE symbol) {
  if (expect_string(name, "maybe you forgot to quote your strings?") == false) {
    mark_pos();
    return false;
  }
  return callback(symbol, NULL, level);
}

void JSON::mark_pos() {
  assert((mark == start || *(mark - 1)) != 0, "buffer overrun");
  assert(mark <= pos, "mark runahead");

  u_char c;

  while (mark < pos) {
    c = *mark;
    assert(c != 0, "pos buffer overrun?");
    if (c != 0) {
      mark++;
      column++;
    }
    if (c == '\n') {
      line++;
      column = 0;
    }
  }

  assert(mark <= pos, "mark runahead");
}

u_char JSON::next() {
  assert((pos == start || *(pos - 1)) != 0, "buffer overrun");

  u_char c = *pos;
  if (c != 0) {
    pos++;
  }
  return c;
}

u_char JSON::peek() {
  return *pos;
}

// Peek ahead i chars (0 is same as peek())
u_char JSON::peek(size_t i) {
  u_char c;
  const char* p;

  p = pos;
  c = *p;
  while (i > 0 && c != 0) {
    i--;
    p++;
    c = *p;
  }
  return c;
}

/*
* Check that one of the expected characters is next in the stream.
* If not, it is an error.
* Returns 0 if EOS is encountered.
* Returns -1 if the next character was not one of the expected.
* Otherwise consumes and returns the expected character that was encountered.
*/
int JSON::expect_any(const char* valid_chars, const char* error_msg, JSON_ERROR e) {
  size_t len;
  u_char c;

  len = strlen(valid_chars);
  assert(len > 0, "need non-empty string");

  c = peek();
  if (c == 0) {
    error(e, "Got EOS when expecting %s (%s\'%s\').", error_msg, len > 1 ? "one of " : "", valid_chars);
    return 0;
  }
  for (size_t i = 0; i < len; i++) {
    if (c == valid_chars[i]) {
      return next();
    }
  }
  error(e, "Expected %s (%s\'%s\').", error_msg, len > 1 ? "one of " : "", valid_chars);
  return -1;
}

/*
* Check that the expected string is next in the stream.
* If not, it is an error.
* Consumes the expected characters if they are present.
* Returns true if the expected characters were present, otherwise false.
*/
bool JSON::expect_string(const char* expected_string, const char* error_msg, JSON_ERROR e) {
  u_char c, expected_char;
  size_t len;

  assert(expected_string != NULL, "need non-null string");
  len = strlen(expected_string);
  assert(len > 0, "need non-empty string");

  for (size_t i = 0; i < len; i++) {
    expected_char = expected_string[i];
    assert(expected_char > ' ', "not sane for control characters");
    if (expected_char <= ' ') {
      error(INTERNAL_ERROR, "expect got a control char");
    }
    c = pos[i];
    if (c == 0) {
      error(e, "EOS encountered when expecting %s (\"%s\")", error_msg, expected_string);
      return false;
    } else if (c != expected_char) {
      error(e, "Expected \"%s\" (%s)", expected_string, error_msg);
      return false;
    }
  }
  skip(len);
  return true;
}

/*
* Skip i characters.
* Returns number of characters skipped.
*/
size_t JSON::skip(size_t i) {
  u_char c;
  size_t j;

  c = peek();
  for (j = i; c != 0 && j > 0; j--) {
    c = next();
  }
  return i - j;
}

/*
* Skip whitespace and comments.
* Returns the first token after whitespace/comments without consuming it
* Returns 0 if EOS is encountered.
* Returns -1 if there is an error
*/
int JSON::skip_to_token() {
  for (;;) {
    int c = peek(0);
    if (c == '/') {
      u_char c2 = peek(1);
      if (c2 == '/') {
        c = skip_line_comment();
      } else if (c2 == '*') {
        c = skip_block_comment();
        if (c < 0) {
          return -1;
        }
      }
      // Fall through to keep checking if there
      // are more whitespace / comments to skip
    }
    if (c == 0 || c > ' ') {
      return c;
    }
    next();
  }
  return 0;
}

/*
* Skip to, and return the wanted char without consuming it
* Returns 0 if EOS is encountered.
*/
u_char JSON::skip_to(u_char want) {
  // We want the bookkeeping done in next().
  // Otherwise strchr could have been used.
  u_char c;
  for(;;) {
    c = peek();
    if (c == 0 || c == want) {
      return c;
    }
    next();
  }
}

/*
* Should only be called when we actually have a line comment to skip.
* Otherwise it is an internal error.
*
* Will return the first token after the line comment without consuming it.
* Returns 0 if EOS is encountered.
*/
u_char JSON::skip_line_comment() {
  u_char c;

  // Check that we are not called in error
  expect_any("/", "line comment start", INTERNAL_ERROR);
  expect_any("/", "line comment start", INTERNAL_ERROR);

  c = skip_to('\n');
  if (c == 0) {
    return 0;
  }
  next();
  return next();
}

/*
* Should only be called when we actually have a block comment to skip.
* Otherwise it is an internal error.
*
* Returns the first token after the block comment without consuming it.
* Returns -1 if EOS is encountered in the middle of a comment.
*/
int JSON::skip_block_comment() {
  const char* current;

  // Check that we are not called in error.
  if (peek() != '/' || peek(1) != '*') {
    // Let expect handle EOS.
    expect_string("/*", "block comment start", INTERNAL_ERROR);
    return 0;
  }

  current = pos;
  for (;;) {
    current = strchrnul_(current, '*');

    if (current[0] == 0 || current[1] == 0) {
      // Advance error marker to start of block comment
      mark_pos();
      error(SYNTAX_ERROR, "Block comment started here never ended. Expected \"*/\" before EOS.");
      return -1;
    }

    if (current[1] == '/') {
      pos = current;
      if (expect_string("*/", "block comment end", INTERNAL_ERROR) == false) {
        return -1;
      }
      // Found block comment end
      return peek();
    }
    current++;
  }
}

const char* JSON::strerror(JSON_ERROR e) {
  switch (e) {
  case SYNTAX_ERROR:
    return "Syntax error";
  case INTERNAL_ERROR:
    return "Internal error";
  case KEY_ERROR:
    return "Key error";
  case VALUE_ERROR:
    return "Value error";
  default:
    ShouldNotReachHere();
    return "Unknown error";
  }
}

void JSON::error(JSON_ERROR e, const char* format, ...) {
  _valid = false;

  if (!silent) {
    const char* line_start;
    const char* tmp;
    size_t line_length;
    va_list args;
    u_char c;

    _st->print("%s on line %u byte %u: ", JSON::strerror(e), line, column + 1);
    va_start(args, format);
    _st->vprint(format, args);
    _st->cr();
    va_end(args);

    line_start = mark - column;
    assert(line_start >= start, "out of bounds");
    assert(line_start <= mark, "out of bounds");
    assert(line_start == start || line_start[-1] == '\n', "line counting error");

    c = *pos;
    if (c == 0) {
      _st->print(" Got ");
      _st->print_cr("EOS.");
    }
    tmp = mark;
    c = *tmp;
    if (c > ' ') {
      _st->print(" At ");
      _st->print("'");
      while (c > ' ') {
        _st->print("%c", c);
        tmp++;
        c = *tmp;
      }
      _st->print_cr("'.");
    }

    // Skip to newline or EOS
    tmp = strchrnul_(mark, '\n');
    line_length = tmp - line_start;

    _st->print_cr("%s", line_start);
  }
}

¤ Dauer der Verarbeitung: 0.29 Sekunden (vorverarbeitet) ¤

Download des Quellennavigators
Download des sprechenden Kalenders
in der Quellcodebibliothek suchen

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.