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.

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()

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

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.open(json) ⇒ 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.

@param [String] json JSON document string

method call

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()

Yield Parameters:

  • doc (Oj::Doc)

    parsed JSON document

Yield Returns:

  • (Object)

    returns the result of the yield as the result of the


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# File 'ext/oj/fast.c', line 1106

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

    Check_Type(str, T_STRING);
    len      = (int)RSTRING_LEN(str) + 1;
    allocate = (SMALL_JSON < len || !given);
    if (allocate) {
        json = ALLOC_N(char, len);
    } else {
        json = ALLOCA_N(char, len);
    }
    // It should not be necessaary to stop GC but if it is not stopped and a
    // large string is parsed that string is corrupted or freed during
    // parsing. I'm not sure what is going on exactly but disabling GC avoids
    // the issue.
    rb_gc_disable();
    memcpy(json, StringValuePtr(str), len);
    obj = parse_json(clas, json, given, allocate);
    rb_gc_enable();
    if (given && allocate) {
        xfree(json);
    }
    return obj;
}

.open_file(filename) ⇒ 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.

@param [String] filename name of file that contains a JSON document

method call

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()

Yield Parameters:

  • doc (Oj::Doc)

    parsed JSON document

Yield Returns:

  • (Object)

    returns the result of the yield as the result of the


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# File 'ext/oj/fast.c', line 1154

static VALUE doc_open_file(VALUE clas, VALUE filename) {
    char *         path;
    char *         json;
    FILE *         f;
    size_t         len;
    volatile 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_JSON < 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';
    rb_gc_disable();
    obj = parse_json(clas, json, given, allocate);
    rb_gc_enable();
    if (given && allocate) {
        xfree(json);
    }
    return obj;
}

.open(json) ⇒ 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.

@param [String] json JSON document string

method call

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()

Yield Parameters:

  • doc (Oj::Doc)

    parsed JSON document

Yield Returns:

  • (Object)

    returns the result of the yield as the result of the


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# File 'ext/oj/fast.c', line 1106

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

    Check_Type(str, T_STRING);
    len      = (int)RSTRING_LEN(str) + 1;
    allocate = (SMALL_JSON < len || !given);
    if (allocate) {
        json = ALLOC_N(char, len);
    } else {
        json = ALLOCA_N(char, len);
    }
    // It should not be necessaary to stop GC but if it is not stopped and a
    // large string is parsed that string is corrupted or freed during
    // parsing. I'm not sure what is going on exactly but disabling GC avoids
    // the issue.
    rb_gc_disable();
    memcpy(json, StringValuePtr(str), len);
    obj = parse_json(clas, json, given, allocate);
    rb_gc_enable();
    if (given && allocate) {
        xfree(json);
    }
    return obj;
}

Instance Method Details

#cloneObject


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# File 'ext/oj/fast.c', line 1645

static VALUE doc_not_implemented(VALUE self) {
    rb_raise(rb_eNotImpError, "Not implemented.");
    return Qnil;
}

#closeObject

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()

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# File 'ext/oj/fast.c', line 1628

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);
        xfree(doc);
    }
    return Qnil;
}

#dump(path, filename) ⇒ Object

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

@param path [String] if provided it identified the top of the branch to

dump to JSON

@param filename [String] if provided it is the filename to write the output

to

Examples:

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

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# File 'ext/oj/fast.c', line 1566

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))) {
        volatile VALUE rjson;

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

            out.buf       = buf;
            out.end       = buf + sizeof(buf) - 10;
            out.allocated = false;
            out.omit_nil  = oj_default_options.dump_opts.omit_nil;
            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;
}

#dupObject


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# File 'ext/oj/fast.c', line 1645

static VALUE doc_not_implemented(VALUE self) {
    rb_raise(rb_eNotImpError, "Not implemented.");
    return Qnil;
}

#each_child(path = nil) ⇒ Object

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.

@param [String] path if provided it identified the top of the branch to

process the chilren of

Examples:

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

Yield Parameters:

  • Doc (Doc)

    at the child location


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# File 'ext/oj/fast.c', line 1468

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 + 1));
        }
        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 + 1));
                }
                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 + 1));
        }
    }
    return Qnil;
}

#each_leaf(path = nil) ⇒ Object

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.

@param [String] path if provided it identified the top of the branch to

process the leaves of

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]

Yield Parameters:

  • Doc (Doc)

    at the child location


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# File 'ext/oj/fast.c', line 1392

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 + 1));
        }
        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 + 1));
                }
                return Qnil;
            }
        }
        each_leaf(doc, self);
        if (0 < wlen) {
            memcpy(doc->where_path, save_path, sizeof(Leaf) * (wlen + 1));
        }
    }
    return Qnil;
}

#each_value(path = nil) ⇒ Object

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.

@param [String] path if provided it identified the top of the branch to

process the leaf values of

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]

Yield Parameters:

  • val (Object)

    each leaf value


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# File 'ext/oj/fast.c', line 1535

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) ⇒ Object

Hash

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.

@param [String] path path to the location to get the type of if provided

Examples:

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

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# File 'ext/oj/fast.c', line 1356

static VALUE doc_fetch(int argc, VALUE *argv, VALUE self) {
    Doc            doc;
    Leaf           leaf;
    volatile 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;
}

#homeObject

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? }

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

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_keyObject

Returns the final key to the current location. “one” Oj::Doc.open(‘') { |doc| doc.local_key() } #=> nil

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() }  #=>

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# File 'ext/oj/fast.c', line 1271

static VALUE doc_local_key(VALUE self) {
    Doc            doc  = self_doc(self);
    Leaf           leaf = *doc->where;
    volatile 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) ⇒ Object

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

@param [String] path path to the location to move to

“/one/2”

Examples:

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

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# File 'ext/oj/fast.c', line 1434

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;
}

#sizeObject

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:

  • Returns the size of the JSON document.


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# File 'ext/oj/fast.c', line 1615

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

#type(path = nil) ⇒ Object

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.

@param [String] path path to the location to get the type of if provided

Examples:

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

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# File 'ext/oj/fast.c', line 1313

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->rtype) {
        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;
#ifdef RUBY_INTEGER_UNIFICATION
        case T_FIXNUM: type = rb_cInteger; break;
#else
        case T_FIXNUM: type = rb_cFixnum; break;
#endif
        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?Boolean

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

Returns:

  • (Boolean)

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# File 'ext/oj/fast.c', line 1225

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 += esc_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 = append_key(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);
    }
}