class Oj::Doc
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.
@example
json = %Q{[ { "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()
Public Class Methods
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 @yieldparam [Oj::Doc] doc parsed JSON document @yieldreturn [Object] returns the result of the yield as the result of the method call @example
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()
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; }
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 @yieldparam [Oj::Doc] doc parsed JSON document @yieldreturn [Object] returns the result of the yield as the result of the method call @example
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()
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; }
@see ::open
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; }
Public Instance Methods
Closes an open document. No further calls to the document will be valid after closing. @example
doc = Oj::Doc.open('[1,2,3]') doc.size() #=> 4 doc.close()
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; }
Dumps the document or nodes to a new JSON document. It uses the default options for generating the JSON. @param [String] path if provided it identified the top of the branch to dump to JSON @param [String] filename if provided it is the filename to write the output to @example
Oj::Doc.open('[3,[2,1]]') { |doc| doc.dump('/2') } #=> "[2,1]"
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; }
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 @yieldparam [Doc] Doc at the child location @example
Oj::Doc.open('[3,[2,1]]') { |doc| result = [] doc.each_value('/2') { |doc| result << doc.where? } result } #=> ["/2/1", "/2/2"]
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; }
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 @yieldparam [Doc] Doc at the child location @example
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]
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; }
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 @yieldparam [Object] val each leaf value @example
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]
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; }
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 @example
Oj::Doc.open('[1,2]') { |doc| doc.fetch() } #=> [1, 2] Oj::Doc.open('[1,2]') { |doc| doc.fetch('/1') } #=> 1
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; }
Moves the document marker or location to the hoot or home position. The same operation can be performed with a #move('/'). @example
Oj::Doc.open('[1,2,3]') { |doc| doc.move('/2'); doc.home(); doc.where? } #=> '/'
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; }
Returns the final key to the current location. @example
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
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; }
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 @example
Oj::Doc.open('{"one":[1,2]') { |doc| doc.move('/one/2'); doc.where? } #=> "/one/2"
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; }
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 @example
Oj::Doc.open('[1,2]') { |doc| doc.type() } #=> Array Oj::Doc.open('[1,2]') { |doc| doc.type('/1') } #=> Fixnum
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; 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; }
Returns a String that describes the absolute path to the current location in the JSON document.
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); } }