pycodec

func Compact ¶

func Compact(dst *bytes.Buffer, src []byte) error

Compact appends to dst the PYCODEC-encoded src with insignificant space characters elided.

func HTMLEscape ¶

func HTMLEscape(dst *bytes.Buffer, src []byte)

HTMLEscape appends to dst the PYCODEC-encoded src with <, >, &, U+2028 and U+2029 characters inside string literals changed to \u003c, \u003e, \u0026, \u2028, \u2029 so that the PYCODEC will be safe to embed inside HTML <script> tags. For historical reasons, web browsers don't honor standard HTML escaping within <script> tags, so an alternative PYCODEC encoding must be used.

func Indent ¶

func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error

Indent appends to dst an indented form of the PYCODEC-encoded src. Each element in a PYCODEC object or array begins on a new, indented line beginning with prefix followed by one or more copies of indent according to the indentation nesting. The data appended to dst does not begin with the prefix nor any indentation, to make it easier to embed inside other formatted PYCODEC data. Although leading space characters (space, tab, carriage return, newline) at the beginning of src are dropped, trailing space characters at the end of src are preserved and copied to dst. For example, if src has no trailing spaces, neither will dst; if src ends in a trailing newline, so will dst.

func Marshal ¶

func Marshal(v interface{}) ([]byte, error)

Marshal returns the PYCODEC encoding of v.

Marshal traverses the value v recursively. If an encountered value implements the Marshaler interface and is not a nil pointer, Marshal calls its MarshalPYCODEC method to produce PYCODEC. If no MarshalPYCODEC method is present but the value implements encoding.TextMarshaler instead, Marshal calls its MarshalText method and encodes the result as a PYCODEC string. The nil pointer exception is not strictly necessary but mimics a similar, necessary exception in the behavior of UnmarshalPYCODEC.

Otherwise, Marshal uses the following type-dependent default encodings:

Boolean values encode as PYCODEC booleans.

Floating point, integer, and Number values encode as PYCODEC numbers.

String values encode as PYCODEC strings coerced to valid UTF-8, replacing invalid bytes with the Unicode replacement rune. The angle brackets "<" and ">" are escaped to "\u003c" and "\u003e" to keep some browsers from misinterpreting PYCODEC output as HTML. Ampersand "&" is also escaped to "\u0026" for the same reason. This escaping can be disabled using an Encoder that had SetEscapeHTML(false) called on it.

Array and slice values encode as PYCODEC arrays, except that []byte encodes as a base64-encoded string, and a nil slice encodes as the null PYCODEC value.

Struct values encode as PYCODEC objects. Each exported struct field becomes a member of the object, using the field name as the object key, unless the field is omitted for one of the reasons given below.

The encoding of each struct field can be customized by the format string stored under the "pycodec" key in the struct field's tag. The format string gives the name of the field, possibly followed by a comma-separated list of options. The name may be empty in order to specify options without overriding the default field name.

The "omitempty" option specifies that the field should be omitted from the encoding if the field has an empty value, defined as false, 0, a nil pointer, a nil interface value, and any empty array, slice, map, or string.

As a special case, if the field tag is "-", the field is always omitted. Note that a field with name "-" can still be generated using the tag "-,".

Examples of struct field tags and their meanings:

// Field appears in PYCODEC as key "myName".
Field int `pycodec:"myName"`

// Field appears in PYCODEC as key "myName" and
// the field is omitted from the object if its value is empty,
// as defined above.
Field int `pycodec:"myName,omitempty"`

// Field appears in PYCODEC as key "Field" (the default), but
// the field is skipped if empty.
// Note the leading comma.
Field int `pycodec:",omitempty"`

// Field is ignored by this package.
Field int `pycodec:"-"`

// Field appears in PYCODEC as key "-".
Field int `pycodec:"-,"`

The "string" option signals that a field is stored as PYCODEC inside a PYCODEC-encoded string. It applies only to fields of string, floating point, integer, or boolean types. This extra level of encoding is sometimes used when communicating with JavaScript programs:

Int64String int64 `pycodec:",string"`

The key name will be used if it's a non-empty string consisting of only Unicode letters, digits, and ASCII punctuation except quotation marks, backslash, and comma.

Anonymous struct fields are usually marshaled as if their inner exported fields were fields in the outer struct, subject to the usual Go visibility rules amended as described in the next paragraph. An anonymous struct field with a name given in its PYCODEC tag is treated as having that name, rather than being anonymous. An anonymous struct field of interface type is treated the same as having that type as its name, rather than being anonymous.

The Go visibility rules for struct fields are amended for PYCODEC when deciding which field to marshal or unmarshal. If there are multiple fields at the same level, and that level is the least nested (and would therefore be the nesting level selected by the usual Go rules), the following extra rules apply:

1) Of those fields, if any are PYCODEC-tagged, only tagged fields are considered, even if there are multiple untagged fields that would otherwise conflict.

2) If there is exactly one field (tagged or not according to the first rule), that is selected.

3) Otherwise there are multiple fields, and all are ignored; no error occurs.

Handling of anonymous struct fields is new in Go 1.1. Prior to Go 1.1, anonymous struct fields were ignored. To force ignoring of an anonymous struct field in both current and earlier versions, give the field a PYCODEC tag of "-".

Map values encode as PYCODEC objects. The map's key type must either be a string, an integer type, or implement encoding.TextMarshaler. The map keys are sorted and used as PYCODEC object keys by applying the following rules, subject to the UTF-8 coercion described for string values above:

• string keys are used directly
• encoding.TextMarshalers are marshaled
• integer keys are converted to strings

Pointer values encode as the value pointed to. A nil pointer encodes as the null PYCODEC value.

Interface values encode as the value contained in the interface. A nil interface value encodes as the null PYCODEC value.

Channel, complex, and function values cannot be encoded in PYCODEC. Attempting to encode such a value causes Marshal to return an UnsupportedTypeError.

PYCODEC cannot represent cyclic data structures and Marshal does not handle them. Passing cyclic structures to Marshal will result in an infinite recursion.

func MarshalIndent ¶

func MarshalIndent(v interface{}, prefix, indent string) ([]byte, error)

MarshalIndent is like Marshal but applies Indent to format the output.

func Unmarshal ¶

func Unmarshal(data []byte, v interface{}) error

Unmarshal parses the PYCODEC-encoded data and stores the result in the value pointed to by v.

Unmarshal uses the inverse of the encodings that Marshal uses, allocating maps, slices, and pointers as necessary, with the following additional rules:

To unmarshal PYCODEC into a pointer, Unmarshal first handles the case of the PYCODEC being the PYCODEC literal null. In that case, Unmarshal sets the pointer to nil. Otherwise, Unmarshal unmarshals the PYCODEC into the value pointed at by the pointer. If the pointer is nil, Unmarshal allocates a new value for it to point to.

To unmarshal PYCODEC into a value implementing the Unmarshaler interface, Unmarshal calls that value's UnmarshalPYCODEC method, including when the input is a PYCODEC null. Otherwise, if the value implements encoding.TextUnmarshaler and the input is a PYCODEC quoted string, Unmarshal calls that value's UnmarshalText method with the unquoted form of the string.

To unmarshal PYCODEC into a struct, Unmarshal matches incoming object keys to the keys used by Marshal (either the struct field name or its tag), preferring an exact match but also accepting a case-insensitive match. Unmarshal will only set exported fields of the struct.

To unmarshal PYCODEC into an interface value, Unmarshal stores one of these in the interface value:

bool, for PYCODEC booleans
float64, for PYCODEC numbers
string, for PYCODEC strings
[]interface{}, for PYCODEC arrays
map[string]interface{}, for PYCODEC objects
nil for PYCODEC null

To unmarshal a PYCODEC array into a slice, Unmarshal resets the slice length to zero and then appends each element to the slice. As a special case, to unmarshal an empty PYCODEC array into a slice, Unmarshal replaces the slice with a new empty slice.

To unmarshal a PYCODEC array into a Go array, Unmarshal decodes PYCODEC array elements into corresponding Go array elements. If the Go array is smaller than the PYCODEC array, the additional PYCODEC array elements are discarded. If the PYCODEC array is smaller than the Go array, the additional Go array elements are set to zero values.

To unmarshal a PYCODEC object into a map, Unmarshal first establishes a map to use. If the map is nil, Unmarshal allocates a new map. Otherwise Unmarshal reuses the existing map, keeping existing entries. Unmarshal then stores key-value pairs from the PYCODEC object into the map. The map's key type must either be a string, an integer, or implement encoding.TextUnmarshaler.

If a PYCODEC value is not appropriate for a given target type, or if a PYCODEC number overflows the target type, Unmarshal skips that field and completes the unmarshaling as best it can. If no more serious errors are encountered, Unmarshal returns an UnmarshalTypeError describing the earliest such error.

The PYCODEC null value unmarshals into an interface, map, pointer, or slice by setting that Go value to nil. Because null is often used in PYCODEC to mean “not present,” unmarshaling a PYCODEC null into any other Go type has no effect on the value and produces no error.

When unmarshaling quoted strings, invalid UTF-8 or invalid UTF-16 surrogate pairs are not treated as an error. Instead, they are replaced by the Unicode replacement character U+FFFD.