Class: Oj::Doc

Inherits:
Object
  • Object
show all
Defined in:
ext/oj/fast.c,
ext/oj/fast.c

Overview

The Doc class is used to parse and navigate a JSON document. The model it employs is that of a document that while open can be navigated and values extracted. Once the document is closed the document can not longer be accessed. This allows the parsing and data extraction to be extremely fast compared to other JSON parses.

An Oj::Doc class is not created directly but the _open()_ class method is used to open a document and the yield parameter to the block of the #open() call is the Doc instance. The Doc instance can be moved across, up, and down the JSON document. At each element the data associated with the element can be extracted. It is also possible to just provide a path to the data to be extracted and retrieve the data in that manner.

For many of the methods a path is used to describe the location of an element. Paths follow a subset of the XPath syntax. The slash ('/') character is the separator. Each step in the path identifies the next branch to take through the document. A JSON object will expect a key string while an array will expect a positive index. A .. step indicates a move up the JSON document.

Examples:

json = %{[
  {
    "one"   : 1,
    "two"   : 2
  },
  {
    "three" : 3,
    "four"  : 4
  }
]}
# move and get value
Oj::Doc.open(json) do |doc|
  doc.move('/1/two')
  # doc location is now at the 'two' element of the hash that is the first element of the array.
  doc.fetch()
end
#=> 2

# Now try again using a path to Oj::Doc.fetch() directly and not using a block.
doc = Oj::Doc.open(json)
doc.fetch('/2/three')  #=> 3
doc.close()

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.open(json) {|doc| ... } ⇒ Object

Parses a JSON document String and then yields to the provided block if one is given with an instance of the Oj::Doc as the single yield parameter. If a block is not given then an Oj::Doc instance is returned and must be closed with a call to the #close() method when no longer needed.

Examples:

Oj::Doc.open('[1,2,3]') { |doc| doc.size() }  #=> 4
# or as an alternative
doc = Oj::Doc.open('[1,2,3]')
doc.size()  #=> 4
doc.close()

Yields:

  • (doc)

Returns:

  • (Object)

Parameters:

  • json (String)

    JSON document string

Yield Parameters:

  • doc (Oj::Doc)

    parsed JSON document

Yield Returns:

  • (Object)

    returns the result of the yield as the result of the method call



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# File 'ext/oj/fast.c', line 1116

static VALUE
doc_open(VALUE clas, VALUE str) {
    char	*json;
    size_t	len;
    VALUE	obj;
    int		given = rb_block_given_p();
    int		allocate;

    Check_Type(str, T_STRING);
    len = RSTRING_LEN(str) + 1;
    allocate = (SMALL_XML < len || !given);
    if (allocate) {
	json = ALLOC_N(char, len);
    } else {
	json = ALLOCA_N(char, len);
    }
    memcpy(json, StringValuePtr(str), len);
    obj = parse_json(clas, json, given, allocate);
    if (given && allocate) {
	xfree(json);
    }
    return obj;
}

.open_file(filename) {|doc| ... } ⇒ Object

Parses a JSON document from a file and then yields to the provided block if one is given with an instance of the Oj::Doc as the single yield parameter. If a block is not given then an Oj::Doc instance is returned and must be closed with a call to the #close() method when no longer needed.

Examples:

File.open('array.json', 'w') { |f| f.write('[1,2,3]') }
Oj::Doc.open_file(filename) { |doc| doc.size() }  #=> 4
# or as an alternative
doc = Oj::Doc.open_file(filename)
doc.size()  #=> 4
doc.close()

Yields:

  • (doc)

Returns:

  • (Object)

Parameters:

  • filename (String)

    name of file that contains a JSON document

Yield Parameters:

  • doc (Oj::Doc)

    parsed JSON document

Yield Returns:

  • (Object)

    returns the result of the yield as the result of the method call



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# File 'ext/oj/fast.c', line 1158

static VALUE
doc_open_file(VALUE clas, VALUE filename) {
    char	*path;
    char	*json;
    FILE	*f;
    size_t	len;
    VALUE	obj;
    int		given = rb_block_given_p();
    int		allocate;

    Check_Type(filename, T_STRING);
    path = StringValuePtr(filename);
    if (0 == (f = fopen(path, "r"))) {
	rb_raise(rb_eIOError, "%s", strerror(errno));
    }
    fseek(f, 0, SEEK_END);
    len = ftell(f);
    allocate = (SMALL_XML < len || !given);
    if (allocate) {
	json = ALLOC_N(char, len + 1);
    } else {
	json = ALLOCA_N(char, len + 1);
    }
    fseek(f, 0, SEEK_SET);
    if (len != fread(json, 1, len, f)) {
	fclose(f);
	rb_raise(rb_const_get_at(Oj, rb_intern("LoadError")), 
		 "Failed to read %lu bytes from %s.", (unsigned long)len, path);
    }
    fclose(f);
    json[len] = '\0';
    obj = parse_json(clas, json, given, allocate);
    if (given && allocate) {
	xfree(json);
    }
    return obj;
}

.open(json) {|doc| ... } ⇒ Object

Parses a JSON document String and then yields to the provided block if one is given with an instance of the Oj::Doc as the single yield parameter. If a block is not given then an Oj::Doc instance is returned and must be closed with a call to the #close() method when no longer needed.

Examples:

Oj::Doc.open('[1,2,3]') { |doc| doc.size() }  #=> 4
# or as an alternative
doc = Oj::Doc.open('[1,2,3]')
doc.size()  #=> 4
doc.close()

Yields:

  • (doc)

Returns:

  • (Object)

Parameters:

  • json (String)

    JSON document string

Yield Parameters:

  • doc (Oj::Doc)

    parsed JSON document

Yield Returns:

  • (Object)

    returns the result of the yield as the result of the method call



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# File 'ext/oj/fast.c', line 1116

static VALUE
doc_open(VALUE clas, VALUE str) {
    char	*json;
    size_t	len;
    VALUE	obj;
    int		given = rb_block_given_p();
    int		allocate;

    Check_Type(str, T_STRING);
    len = RSTRING_LEN(str) + 1;
    allocate = (SMALL_XML < len || !given);
    if (allocate) {
	json = ALLOC_N(char, len);
    } else {
	json = ALLOCA_N(char, len);
    }
    memcpy(json, StringValuePtr(str), len);
    obj = parse_json(clas, json, given, allocate);
    if (given && allocate) {
	xfree(json);
    }
    return obj;
}

Instance Method Details

#closenil

Closes an open document. No further calls to the document will be valid after closing.

Examples:

doc = Oj::Doc.open('[1,2,3]')
doc.size()  #=> 4
doc.close()

Returns:

  • (nil)


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# File 'ext/oj/fast.c', line 1604

static VALUE
doc_close(VALUE self) {
    Doc		doc = self_doc(self);

    rb_gc_unregister_address(&doc->self);
    DATA_PTR(doc->self) = 0;
    if (0 != doc) {
	xfree(doc->json);
	doc_free(doc);
    }
    return Qnil;
}

#dump(path = nil) ⇒ String

Dumps the document or nodes to a new JSON document. It uses the default options for generating the JSON.

Examples:

Oj::Doc.open('[3,[2,1]]') { |doc|
    doc.dump('/2')
}
#=> "[2,1]"

Returns:

  • (String)

Parameters:

  • path (String)

    if provided it identified the top of the branch to dump to JSON

  • filename (String)

    if provided it is the filename to write the output to



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# File 'ext/oj/fast.c', line 1541

static VALUE
doc_dump(int argc, VALUE *argv, VALUE self) {
    Doc		doc = self_doc(self);
    Leaf	leaf;
    const char	*path = 0;
    const char	*filename = 0;

    if (1 <= argc) {
	if (Qnil != *argv) {
	    Check_Type(*argv, T_STRING);
	    path = StringValuePtr(*argv);
	}
	if (2 <= argc) {
	    Check_Type(argv[1], T_STRING);
	    filename = StringValuePtr(argv[1]);
	}
    }
    if (0 != (leaf = get_doc_leaf(doc, path))) {
	VALUE	rjson;

	if (0 == filename) {
	    char	buf[4096];
	    struct _Out out;

	    out.buf = buf;
	    out.end = buf + sizeof(buf) - 10;
	    out.allocated = 0;
	    oj_dump_leaf_to_json(leaf, &oj_default_options, &out);
	    rjson = rb_str_new2(out.buf);
	    if (out.allocated) {
		xfree(out.buf);
	    }
	} else {
	    oj_write_leaf_to_file(leaf, filename, &oj_default_options);
	    rjson = Qnil;
	}
	return rjson;
    }
    return Qnil;
}

#each_child(path = nil) {|doc| ... } ⇒ nil

Yields to the provided block for each immediate child node with the identified location of the JSON document as the root. The parameter passed to the block on yield is the Doc instance after moving to the child location.

Examples:

Oj::Doc.open('[3,[2,1]]') { |doc|
    result = []
    doc.each_value('/2') { |doc| result << doc.where? }
    result
}
#=> ["/2/1", "/2/2"]

Yields:

  • (doc)

Returns:

  • (nil)

Parameters:

  • path (String)

    if provided it identified the top of the branch to process the chilren of

Yield Parameters:

  • Doc (Doc)

    at the child location



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# File 'ext/oj/fast.c', line 1444

static VALUE
doc_each_child(int argc, VALUE *argv, VALUE self) {
    if (rb_block_given_p()) {
	Leaf		save_path[MAX_STACK];
	Doc		doc = self_doc(self);
	const char	*path = 0;
	size_t		wlen;

	wlen = doc->where - doc->where_path;
	if (0 < wlen) {
	    memcpy(save_path, doc->where_path, sizeof(Leaf) * wlen);
	}
	if (1 <= argc) {
	    Check_Type(*argv, T_STRING);
	    path = StringValuePtr(*argv);
	    if ('/' == *path) {
		doc->where = doc->where_path;
		path++;
	    }
	    if (0 != move_step(doc, path, 1)) {
		if (0 < wlen) {
		    memcpy(doc->where_path, save_path, sizeof(Leaf) * wlen);
		}
		return Qnil;
	    }
	}
	if (COL_VAL == (*doc->where)->value_type && 0 != (*doc->where)->elements) {
	    Leaf	first = (*doc->where)->elements->next;
	    Leaf	e = first;

	    doc->where++;
	    do {
		*doc->where = e;
		rb_yield(self);
		e = e->next;
	    } while (e != first);
	}
	if (0 < wlen) {
	    memcpy(doc->where_path, save_path, sizeof(Leaf) * wlen);
	}
    }
    return Qnil;
}

#each_leaf(path = nil) ⇒ nil

Yields to the provided block for each leaf node with the identified location of the JSON document as the root. The parameter passed to the block on yield is the Doc instance after moving to the child location.

Examples:

Oj::Doc.open('[3,[2,1]]') { |doc|
    result = {}
    doc.each_leaf() { |d| result[d.where?] = d.fetch() }
    result
}
#=> ["/1" => 3, "/2/1" => 2, "/2/2" => 1]

Returns:

  • (nil)

Parameters:

  • path (String)

    if provided it identified the top of the branch to process the leaves of

Yield Parameters:

  • Doc (Doc)

    at the child location



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# File 'ext/oj/fast.c', line 1368

static VALUE
doc_each_leaf(int argc, VALUE *argv, VALUE self) {
    if (rb_block_given_p()) {
	Leaf		save_path[MAX_STACK];
	Doc		doc = self_doc(self);
	const char	*path = 0;
	size_t		wlen;

	wlen = doc->where - doc->where_path;
	if (0 < wlen) {
	    memcpy(save_path, doc->where_path, sizeof(Leaf) * wlen);
	}
	if (1 <= argc) {
	    Check_Type(*argv, T_STRING);
	    path = StringValuePtr(*argv);
	    if ('/' == *path) {
		doc->where = doc->where_path;
		path++;
	    }
	    if (0 != move_step(doc, path, 1)) {
		if (0 < wlen) {
		    memcpy(doc->where_path, save_path, sizeof(Leaf) * wlen);
		}
		return Qnil;
	    }
	}
	each_leaf(doc, self);
	if (0 < wlen) {
	    memcpy(doc->where_path, save_path, sizeof(Leaf) * wlen);
	}
    }
    return Qnil;
}

#each_value(path = nil) {|val| ... } ⇒ nil

Yields to the provided block for each leaf value in the identified location of the JSON document. The parameter passed to the block on yield is the value of the leaf. Only those leaves below the element specified by the path parameter are processed.

Examples:

Oj::Doc.open('[3,[2,1]]') { |doc|
    result = []
    doc.each_value() { |v| result << v }
    result
}
#=> [3, 2, 1]

Oj::Doc.open('[3,[2,1]]') { |doc|
    result = []
    doc.each_value('/2') { |v| result << v }
    result
}
#=> [2, 1]

Yields:

  • (val)

Returns:

  • (nil)

Parameters:

  • path (String)

    if provided it identified the top of the branch to process the leaf values of

Yield Parameters:

  • val (Object)

    each leaf value



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# File 'ext/oj/fast.c', line 1511

static VALUE
doc_each_value(int argc, VALUE *argv, VALUE self) {
    if (rb_block_given_p()) {
	Doc		doc = self_doc(self);
	const char	*path = 0;
	Leaf		leaf;

	if (1 <= argc) {
	    Check_Type(*argv, T_STRING);
	    path = StringValuePtr(*argv);
	}
	if (0 != (leaf = get_doc_leaf(doc, path))) {
	    each_value(doc, leaf);
	}
    }
    return Qnil;
}

#fetch(path = nil) ⇒ nil, ...

Returns the value at the location identified by the path or the current location if the path is nil or not provided. This method will create and return an Array or Hash if that is the type of Object at the location specified. This is more expensive than navigating to the leaves of the JSON document.

Examples:

Oj::Doc.open('[1,2]') { |doc| doc.fetch() }      #=> [1, 2]
Oj::Doc.open('[1,2]') { |doc| doc.fetch('/1') }  #=> 1

Returns:

  • (nil, true, false, Fixnum, Float, String, Array, Hash)

Parameters:

  • path (String)

    path to the location to get the type of if provided



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# File 'ext/oj/fast.c', line 1332

static VALUE
doc_fetch(int argc, VALUE *argv, VALUE self) {
    Doc		doc;
    Leaf	leaf;
    VALUE	val = Qnil;
    const char	*path = 0;

    doc = self_doc(self);
    if (1 <= argc) {
	Check_Type(*argv, T_STRING);
	path = StringValuePtr(*argv);
	if (2 == argc) {
	    val = argv[1];
	}
    }
    if (0 != (leaf = get_doc_leaf(doc, path))) {
	val = leaf_value(doc, leaf);
    }
    return val;
}

#homenil

Moves the document marker or location to the hoot or home position. The same operation can be performed with a Oj::Doc.move('/').

Examples:

Oj::Doc.open('[1,2,3]') { |doc| doc.move('/2'); doc.home(); doc.where? }  #=> '/'

Returns:

  • (nil)


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# File 'ext/oj/fast.c', line 1272

static VALUE
doc_home(VALUE self) {
    Doc	doc = self_doc(self);

    *doc->where_path = doc->data;
    doc->where = doc->where_path;

    return oj_slash_string;
}

#local_keyString, ...

Returns the final key to the current location.

Examples:

Oj::Doc.open('[1,2,3]') { |doc| doc.move('/2'); doc.local_key() }	    #=> 2
Oj::Doc.open('{"one":3}') { |doc| doc.move('/one'); doc.local_key() }  #=> "one"
Oj::Doc.open('[1,2,3]') { |doc| doc.local_key() }			    #=> nil

Returns:

  • (String, Fixnum, nil)


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# File 'ext/oj/fast.c', line 1250

static VALUE
doc_local_key(VALUE self) {
    Doc		doc = self_doc(self);
    Leaf	leaf = *doc->where;
    VALUE	key = Qnil;

    if (T_HASH == leaf->parent_type) {
	key = rb_str_new2(leaf->key);
	key = oj_encode(key);
    } else if (T_ARRAY == leaf->parent_type) {
	key = LONG2NUM(leaf->index);
    }
    return key;
}

#move(path) ⇒ nil

Moves the document marker to the path specified. The path can an absolute path or a relative path.

Examples:

Oj::Doc.open('{"one":[1,2]') { |doc| doc.move('/one/2'); doc.where? }  #=> "/one/2"

Returns:

  • (nil)

Parameters:

  • path (String)

    path to the location to move to



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# File 'ext/oj/fast.c', line 1410

static VALUE
doc_move(VALUE self, VALUE str) {
    Doc		doc = self_doc(self);
    const char	*path;
    int		loc;

    Check_Type(str, T_STRING);
    path = StringValuePtr(str);
    if ('/' == *path) {
	doc->where = doc->where_path;
	path++;
    }
    if (0 != (loc = move_step(doc, path, 1))) {
	rb_raise(rb_eArgError, "Failed to locate element %d of the path %s.", loc, path);
    }
    return Qnil;
}

#sizeFixnum

Returns the number of nodes in the JSON document where a node is any one of the basic JSON components.

Examples:

Oj::Doc.open('[1,2,3]') { |doc| doc.size() }  #=> 4

Returns:

  • (Fixnum)

Returns:

  • Returns the size of the JSON document.



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# File 'ext/oj/fast.c', line 1590

static VALUE
doc_size(VALUE self) {
    return ULONG2NUM(((Doc)DATA_PTR(self))->size);
}

#type(path = nil) ⇒ Class

Returns the Class of the data value at the location identified by the path or the current location if the path is nil or not provided. This method does not create the Ruby Object at the location specified so the overhead is low.

Examples:

Oj::Doc.open('[1,2]') { |doc| doc.type() }	     #=> Array
Oj::Doc.open('[1,2]') { |doc| doc.type('/1') }  #=> Fixnum

Returns:

  • (Class)

Parameters:

  • path (String)

    path to the location to get the type of if provided



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# File 'ext/oj/fast.c', line 1293

static VALUE
doc_type(int argc, VALUE *argv, VALUE self) {
    Doc		doc = self_doc(self);
    Leaf	leaf;
    const char	*path = 0;
    VALUE	type = Qnil;

    if (1 <= argc) {
	Check_Type(*argv, T_STRING);
	path = StringValuePtr(*argv);
    }
    if (0 != (leaf = get_doc_leaf(doc, path))) {
	switch (leaf->type) {
	case T_NIL:	type = rb_cNilClass;	break;
	case T_TRUE:	type = rb_cTrueClass;	break;
	case T_FALSE:	type = rb_cFalseClass;	break;
	case T_STRING:	type = rb_cString;	break;
	case T_FIXNUM:	type = rb_cFixnum;	break;
	case T_FLOAT:	type = rb_cFloat;	break;
	case T_ARRAY:	type = rb_cArray;	break;
	case T_HASH:	type = rb_cHash;	break;
	default:				break;
	}
    }
    return type;
}

#where?String

Returns a String that describes the absolute path to the current location in the JSON document.

Returns:

  • (String)

Returns:

  • (Boolean)


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# File 'ext/oj/fast.c', line 1205

static VALUE
doc_where(VALUE self) {
    Doc	doc = self_doc(self);

    if (0 == *doc->where_path || doc->where == doc->where_path) {
	return oj_slash_string;
    } else {
	Leaf	*lp;
	Leaf	leaf;
	size_t	size = 3; // leading / and terminating \0
	char	*path;
	char	*p;

	for (lp = doc->where_path; lp <= doc->where; lp++) {
	    leaf = *lp;
	    if (T_HASH == leaf->parent_type) {
		size += strlen((*lp)->key) + 1;
	    } else if (T_ARRAY == leaf->parent_type) {
		size += ((*lp)->index < 100) ? 3 : 11;
	    }
	}
	path = ALLOCA_N(char, size);
	p = path;
	for (lp = doc->where_path; lp <= doc->where; lp++) {
	    leaf = *lp;
	    if (T_HASH == leaf->parent_type) {
		p = stpcpy(p, (*lp)->key);
	    } else if (T_ARRAY == leaf->parent_type) {
		p = ulong_fill(p, (*lp)->index);
	    }
	    *p++ = '/';
	}
	*--p = '\0';
	return rb_str_new(path, p - path);
    }
}