ogdl

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Published: Feb 1, 2018 License: ISC Imports: 19 Imported by: 26

README

OGDL for Go

Package ogdl is used to process OGDL, the Ordered Graph Data Language.

OGDL is a textual format to write trees or graphs of text, where indentation and spaces define the structure. Here is an example:

network
  ip 192.168.1.100
  gw 192.168.1.9

The language is simple, either in its textual representation or its number of productions (the specification rules), allowing for compact implementations.

OGDL character streams are normally formed by Unicode characters, and encoded as UTF-8 strings, but any encoding that is ASCII transparent is compatible with the specification and the implementations.

This implementation does not support cyles (OGDL Level 2).

Documentation

The documentation of the package is kindly generated by godoc.org.

Installation

go get github.com/rveen/ogdl

Discussion

Use the ogdl-go list, if necessary.

Example: a configuration file

If we have a text file 'conf.g' like this:

eth0
  ip
    192.168.1.1
  gateway
    192.168.1.10
  mask
    255.255.255.0
  timeout
    20

then,

g := ogdl.FromFile("conf.g")
ip := g.Get("eth0.ip").String()
to := g.Get("eth0.timeout").Int64(60)
println("ip:",ip,", timeout:",to)

will print

ip: 192.168.1.1, timeout: 20

If the timeout parameter were not present, then the default value (60) will be assigned to 'to'.

Documentation

Overview

Package ogdl is used to process OGDL, the Ordered Graph Data Language.

OGDL is a textual format to write trees or graphs of text, where indentation and spaces define the structure. Here is an example:

network
  ip 192.168.1.100
  gw 192.168.1.9

The languange is simple, either in its textual representation or its number of productions (the specification rules), allowing for compact implementations.

OGDL character streams are normally formed by Unicode characters, and encoded as UTF-8 strings, but any encoding that is ASCII transparent is compatible with the specification.

See the full spec at http://ogdl.org.

Installation

To install this package just do:

go get github.com/rveen/ogdl

An example

If we have a text file 'config.g' containing:

eth0
  ip
    192.168.1.1
  gateway
    192.168.1.10
  mask
    255.255.255.0
  timeout
    20

then,

g := ogdl.FromFile("config.g")
ip := g.Get("eth0.ip").String()
to := g.Get("eth0.timeout").Int64(60)

println("ip:",ip,", timeout:",to)

will print

ip: 192.168.1.1, timeout: 20

If the timeout parameter was not present, then the default value (60) will be assigned to 'to'. The default value is optional, but be aware that Int64() will return 0 in case that the parameter doesn't exist.

The configuration file can be written in a conciser way:

eth0
  ip      192.168.1.1
  gateway 192.168.1.10
  mask    255.255.255.0
  timeout 20

A template example

The package includes a template processor. It takes an arbitrary input stream with some variables in it, and produces an output stream with the variables resolved out of a Graph object which acts as context.

For example (given the previous config file):

g := ogdl.FromFile("config.g")
t := ogdl.NewTemplate("The gateway's IP is $eth0.gateway")
b := t.Process(g)

string(b) is then:

The gateway's IP is 192.168.1.10

Function signature conventions

Some rules are followed:

.<Type>()      Return the first subnode content converted to the specified type.

.This<Type>()  Return the node content itself converted to the specified type.

.Get()         Return the specified path as a (possible nil) *Graph object.

.Get<Type>()   Return the specified path converted to the specified type.
               These series of functions return value and error.

Index

Examples

Constants

View Source
const (
	TypeExpression = "!e"
	TypePath       = "!p"
	TypeVariable   = "!v"
	TypeSelector   = "!s"
	TypeIndex      = "!i"
	TypeGroup      = "!g"
	TypeTemplate   = "!t"
	TypeString     = "!string"

	TypeIf    = "!if"
	TypeEnd   = "!end"
	TypeElse  = "!else"
	TypeFor   = "!for"
	TypeBreak = "!break"
)

Nodes containing these strings are special

Variables

This section is empty.

Functions

func TCPRawServer

func TCPRawServer(host string, handler func(c net.Conn, b []byte) []byte, timeout int) error

func TCPServerV1

func TCPServerV1(host string, handler func(net.Conn, *Graph) *Graph, timeout int) error

func TCPServerV2

func TCPServerV2(host string, handler func(net.Conn, *Graph) *Graph, timeout int) error

Types

type Graph

type Graph struct {
	This interface{}
	Out  []*Graph
}

Graph is a node with outgoing pointers to other Graph objects. It is implemented as a named list.

func FromBinary

func FromBinary(b []byte) *Graph

FromBinary converts an OGDL binary stream of bytes into a Graph.

func FromBinaryFile

func FromBinaryFile(file string) *Graph

FromBinaryFile converts an OGDL binary stream of bytes into a Graph.

func FromBinaryReader

func FromBinaryReader(r io.Reader) *Graph

FromBinaryReader converts an OGDL binary stream of bytes into a Graph.

func FromBytes

func FromBytes(b []byte) *Graph

FromBytes parses OGDL text contained in a byte array. It returns a *Graph

func FromFile

func FromFile(s string) *Graph

FromFile parses OGDL text contained in a file. It returns a Graph

func FromJSON

func FromJSON(buf []byte) (*Graph, error)

FromJSON converts a JSON text stream into OGDL

Json types returned by Unmashal: bool, for JSON booleans float64, for JSON numbers string, for JSON strings []interface{}, for JSON arrays map[string]interface{}, for JSON objects nil for JSON null

func FromReader

func FromReader(r io.Reader) *Graph

FromReader parses OGDL text coming from a generic io.Reader

func FromString

func FromString(s string) *Graph

FromString parses OGDL text from the given string. It returns a *Graph

func New

func New(n ...interface{}) *Graph

New returns a pointer to Graph, which will be either empty or contain the (optional) object given.

func NewExpression

func NewExpression(s string) *Graph

NewExpression parses an expression in text format (given in the string) to a Graph, in the form of a suitable syntax tree.

expression := expr1 (op2 expr1)*
expr1 := path | constant | op1 path | op1 constant | '(' expr ')' | op1 '(' expr ')'
constant ::= quoted | number
Example
e := NewExpression("1-2+3")
g := New()
i := g.Eval(e)

fmt.Println(i)
Output:

2

func NewPath

func NewPath(s string) *Graph

NewPath takes a Unicode string representing an OGDL path, parses it and returns it as a Graph object.

It also parses extended paths, as those used in templates, which may have argument lists.

func NewTemplate

func NewTemplate(s string) *Graph

NewTemplate parses a text template given as a string and converts it to a Graph. Templates have fixed and variable parts. Variables all begin with '$'.

A template is a text file in any format: plain text, HTML, XML, OGDL or whatever. The dolar sign acts as an escape character that switches from the text to the variable plane. Parsed templates are converted back to text by evaluating the variable parts against a Graph object, by means of the Process() method.

Template grammar

template ::= ( text | variable )*

variable ::= ('$' path) | ('$' '(' expression ')') | ('$' '{' expression '}')
path ::= as defined in path.go
expression ::= as defined in expression.go

Some variables act as directives: $if, $else, $end, $for, $break.

$if(expression)
$else
$end

$for(destPath,sourcepath)
  $break
$end
Example
p := NewTemplate("Hello, $user")

g := New()
g.Add("user").Add("Jenny")

fmt.Println(string(p.Process(g)))
Output:

Hello, Jenny

func NewTemplateFromBytes

func NewTemplateFromBytes(b []byte) *Graph

NewTemplateBytes has the same function as NewTemplate except that the input stream is a byte array.

func (*Graph) Add

func (g *Graph) Add(n interface{}) *Graph

Add adds a subnode to the current node. If the node to be added is a Graph, it is added as is, else it is wrapped in a newly created Graph object.

func (*Graph) AddNodes

func (g *Graph) AddNodes(g2 *Graph) *Graph

AddNodes adds subnodes of the given Graph to the current node.

func (*Graph) Binary

func (g *Graph) Binary() []byte

Binary converts a Graph to a binary OGDL byte stream.

func (*Graph) Bool

func (g *Graph) Bool() bool

Bool returns the node as a boolean. If the node is not a boolean, it returns false, or the default value if given.

func (*Graph) Bytes

func (g *Graph) Bytes() []byte

Bytes returns the graph as []byte, or nil if not possble.

func (*Graph) Check

func (g *Graph) Check(x *Graph) (bool, string)

Check returns true if the Graph given as a parameter conforms to the schema represented by the receiver Graph.

Example
schema := FromString("a !int, b !string, c !float, d !bool")
g := FromString("a 1, b s, c 1.0, d true")

b, message := schema.Check(g)
fmt.Println(b, message)
Output:

true

func (*Graph) Clear

func (g *Graph) Clear()

Clear removes all subnodes

func (*Graph) Clone

func (g *Graph) Clone() *Graph

Clone returns a copy of the current graph.

Warning (from the Go faq): Copying an interface value makes a copy of the thing stored in the interface value. If the interface value holds a struct, copying the interface value makes a copy of the struct. If the interface value holds a pointer, copying the interface value makes a copy of the pointer, but not the data it points to.

func (*Graph) Copy

func (g *Graph) Copy(c *Graph)

Copy adds a copy of the graph given to the current graph.

Warning (from the Go faq): Copying an interface value makes a copy of the thing stored in the interface value. If the interface value holds a struct, copying the interface value makes a copy of the struct. If the interface value holds a pointer, copying the interface value makes a copy of the pointer, but not the data it points to.

func (*Graph) Create

func (g *Graph) Create(s string) *Graph

Create returns the first subnode whose string value is equal to the given string, with its subnodes deleted. If not found, the node is created and returned.

func (*Graph) Delete

func (g *Graph) Delete(n interface{})

Delete removes all subnodes with the given content

func (*Graph) DeleteAt

func (g *Graph) DeleteAt(i int)

DeleteAt removes a subnode by index

func (*Graph) Depth

func (g *Graph) Depth() int

Depth returns the depth of the graph if it is a tree, or -1 if it has cycles.

TODO: Cycles are inferred if level>100, but nodes traversed are not remembered (they should if cycles need to be detected).

func (*Graph) Equals

func (g *Graph) Equals(c *Graph) bool

Equals returns true if the given graph and the receiver graph are equal.

func (*Graph) Eval

func (g *Graph) Eval(e *Graph) interface{}

Eval takes a parsed expression and evaluates it in the context of the current graph.

Example
g := New()
g.Add("a").Add(4)
g.Add("b").Add("4")
e := NewExpression("a+3")
e2 := NewExpression("b+3")
fmt.Println(g.Eval(e))
fmt.Println(g.Eval(e2))
Output:

7
43

func (*Graph) Find

func (g *Graph) Find(re string) (*Graph, error)

Find returns a Graph with all subnodes that match the regular expression given. It only walks through the subnodes of the current Graph. If the regex doesn't compile, an error will be returned. If the result set is empty, both return values are nil (no error is signaled).

func (*Graph) Float64

func (g *Graph) Float64(def ...float64) float64

Float64 returns the node as a float64. If the node is not a number, it returns NaN, or the default value if given.

func (*Graph) Get

func (g *Graph) Get(s string) *Graph

Get recurses a Graph following a given path and returns the result.

This function returns a *Graph in any condition. When there is nothing to return, a nil Graph is returned. This behavior is designed so that the next function in a chain never gets an invalid receiver, avoiding null pointer errors.

OGDL Path: elements are separated by '.' or [] or {} index := [N] selector := {N} tokens can be quoted

Example
g := FromString("a\n b 1\n c 2\n b 3")
fmt.Println(g.Get("a.b{0}").Text())
fmt.Println(g.Get("a.b{1}").Text())
fmt.Println("---")
fmt.Println(g.Get("a.b{}").Text())
fmt.Println("---")
fmt.Println(g.Get("a[0]").Text())
Output:

1
3
---
1
3
---
b
  1

func (*Graph) GetAt

func (g *Graph) GetAt(i int) *Graph

GetAt returns a subnode by index, or nil if the index is out of range.

func (*Graph) GetBool

func (g *Graph) GetBool(path string) (bool, error)

GetBool returns the result of applying a path to the given Graph. The result is returned as a bool. If the path result cannot be converted to a boolean, then an error is returned.

func (*Graph) GetBytes

func (g *Graph) GetBytes(path string) ([]byte, error)

GetBytes returns the result of applying a path to the given Graph. The result is returned as a byte slice.

func (*Graph) GetFloat64

func (g *Graph) GetFloat64(path string) (float64, error)

GetFloat64 returns the result of applying a path to the given Graph. The result is returned as a float64. If the path result cannot be converted to a float, then an error is returned.

func (*Graph) GetInt64

func (g *Graph) GetInt64(path string) (int64, error)

GetInt64 returns the result of applying a path to the given Graph. The result is returned as an int64. If the path result cannot be converted to an integer, then an error is returned.

func (*Graph) GetString

func (g *Graph) GetString(path string) (string, error)

GetString returns the result of applying a path to the given Graph. The result is returned as a string. If the error information is not used, then this method is equivalent to Get(path).String()

func (*Graph) Int64

func (g *Graph) Int64(def ...int64) int64

Int64 returns the node as an int64. If the node is not a number, it returns 0, or the default value if given.

func (*Graph) Interface

func (g *Graph) Interface() interface{}

Interface returns the first child of this node as an interface

func (*Graph) IsNil

func (g *Graph) IsNil() bool

IsNil returns true is this node has no content.

func (*Graph) Len

func (g *Graph) Len() int

Len returns the number of subnodes (outgoing edges, out degree) of this node.

func (*Graph) Node

func (g *Graph) Node(s string) *Graph

Node returns the first subnode whose string value is equal to the given string. It returns nil if not found.

func (*Graph) Number

func (g *Graph) Number() interface{}

Number returns either a float64, int64 or nil

func (*Graph) Process

func (tpl *Graph) Process(ctx *Graph) []byte

Process processes the parsed template, returning the resulting text in a byte array. The variable parts are resolved out of the Graph given.

func (*Graph) Scalar

func (g *Graph) Scalar() interface{}

Scalar returns the current node content, reducing the number of types following these rules:

uint* -> int64
int*  -> int64
float* -> float64
byte -> int64
rune -> int64
bool -> bool
string, []byte: if it represents an int or float or bool,
  convert to int64, float64 or bool

Any other type is returned as is.

func (*Graph) Set

func (g *Graph) Set(s string, val interface{}) *Graph

Set sets the first occurrence of the given path to the value given.

TODO: Support indexes

Example
g := FromString("a b c")
g.Set("a.b", "d")

fmt.Println(g.Text())
Output:

a
  b
    d
Example (A)
g := New()

g.Add("R").Add("b")
r := g.Node("R")
r.Set("id", "1")

fmt.Println(g.Text())
Output:

R
  b
  id
    1

func (*Graph) Show

func (g *Graph) Show() string

Show prints the Graph as text including this (the top) node.

func (*Graph) String

func (g *Graph) String(def ...string) string

String returns a string representation of this node, or an empty string. This function doesn't return an error, because it is mostly used in single variable return situations. String accepts one default value, which will be returned instead of an empty string.

func (*Graph) Substitute

func (g *Graph) Substitute(s string, v interface{})

Substitute traverses the graph substituting all nodes with content equal to s by v.

func (*Graph) Text

func (g *Graph) Text() string

Text is the OGDL text emitter. It converts a Graph into OGDL text.

Strings are quoted if they contain spaces, newlines or special characters. Null elements are not printed, and act as transparent nodes.

BUG():Handle comments correctly. BUG(): 2 times almost the same code:

func (*Graph) ThisBytes

func (g *Graph) ThisBytes() []byte

ThisBytes returns the node as []byte, or nil if not possble.

func (*Graph) ThisInt64

func (g *Graph) ThisInt64() (int64, bool)

ThisInt64 returns a int64 or nil

func (*Graph) ThisNumber

func (g *Graph) ThisNumber() interface{}

ThisNumber returns either a float64, int64 or nil

func (*Graph) ThisScalar

func (g *Graph) ThisScalar() interface{}

ThisScalar returns this node's content as an interface

func (*Graph) ThisString

func (g *Graph) ThisString(def ...string) string

ThisString returns the current node content as a string

func (*Graph) ThisType

func (g *Graph) ThisType() string

ThisType returns the name of the native type contained in the current node.

func (*Graph) ThisValue

func (g *Graph) ThisValue() reflect.Value

ThisValue returns this node as a reflect.Value.

func (*Graph) Value

func (g *Graph) Value() reflect.Value

Value returns the node as a reflect.Value.

type Log

type Log struct {
	// contains filtered or unexported fields
}

Log is a log store for binary OGDL objects.

All objects are appended to a file, and a position is returned.

func OpenLog

func OpenLog(file string) (*Log, error)

OpenLog opens a log file. If the file doesn't exist, it is created.

func (*Log) Add

func (log *Log) Add(g *Graph) int64

Add adds an OGDL object to the log. The starting position into the log is returned.

func (*Log) AddBinary

func (log *Log) AddBinary(b []byte) int64

AddBinary adds an OGDL binary object to the log. The starting position into the log is returned.

func (*Log) Close

func (log *Log) Close()

Close closes a log file

func (*Log) Get

func (log *Log) Get(i int64) (*Graph, int64, error)

Get returns the OGDL object at the position given and the position of the next object, or an error.

func (*Log) GetBinary

func (log *Log) GetBinary(i int64) ([]byte, int64, error)

GetBinary returns the OGDL object at the position given and the position of the next object, or an error. The object returned is in binary form, exactly as it is stored in the log.

func (*Log) Sync

func (log *Log) Sync()

Sync commits the changes to disk (the exact behavior is OS dependent).

type RFunction

type RFunction struct {
	Host     string
	Protocol int
	// contains filtered or unexported fields
}

RFunction represents a remote function (also known as a remote procedure call).

func NewRFunction

func NewRFunction(host string) *RFunction

func (*RFunction) Call

func (rf *RFunction) Call(g *Graph) (*Graph, error)

Call makes a remote call. It sends the given Graph in binary format to the server and returns the response Graph.

func (*RFunction) Close

func (rf *RFunction) Close()

Close closes the underlying connection, if open.

Directories

Path Synopsis
cmd
gpath
gpath <path> [file] Return the specified path from an OGDL file, or from stdin.
gpath <path> [file] Return the specified path from an OGDL file, or from stdin.
gtemplate
gtemplate <template_file> [ogdl_file]* Processes a template file and solves variables in it using data from any of the OGDL files given
gtemplate <template_file> [ogdl_file]* Processes a template file and solves variables in it using data from any of the OGDL files given

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