Tamarin abcFormat
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This document comes from an older version of the Javascript language implementation from the Mozilla project. It describes the compiled format of the ECMAScript version 4 (ECMA-262). Unfortunately, it looks like that document disappeared from the Mozilla website. The implementation can be found (I think) in the Tamarin project (also called Rhino—don't ask me about all these names... I have no clue.) The Tamarin project is what Adobe Flash officially uses for their Javascript player. What I have a hard time to understand is this: it looks like the Tamarin implementation is not in C nor C++ and yet the Flash players don't have 1 megazillion java or whatnot files to install. Hmmmm... They probably have one or two large libraries in some jarball. From the original document, I removed the top Mozilla logo (since you are viewing this page on a different website!) I have changed the broken links to a blue colored text. This gives you an idea of where things were and maybe to find the docs/implementations again. At some point, I will move this information to my reference instead. (See here: SWF Alexis' Reference) Alexis Wilke |
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LXR Roots -
mozilla Cross Reference:
mozilla
mozilla/ js/ tamarin/ core/ abcFormat.txt |
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001 This file stays synchronized with the source code. To view
002 previous formats that we don't support, sync backwards in
003 perforce.
004
005
006 U30 - This is a 30 bit integer value encoded with a variable number of bytes to save space.
007 All U30's are encoded as 1-5 bytes depending on the value (larger values need more space).
008 The encoding method is if the hi bit in the current byte is set, then the next byte is also
009 part of the value. Each bit in a byte contributes 7 bits to the value, with the hi bit telling
010 us whether to use the next byte, or if this is the last byte for the value. This enables us to
011 use 30 bit numbers for everything, but still not take up enormous amounts of space.
012
013 If more than 30 nonzero bits are present for a U30 field, a verify error will occur.
014
015 S32,U32 - same as U30 but 32 bits are allowed instead of being capped at 30.
016
017 The "0" entry of each constant pool is not used. If the count for a given pool says there are
018 "n" entries in the pool, there are "n-1" entries in the file, corresponding to indices 1..(n-1).
019
020 AbcFile {
021 U16 minor_version // = 16 (0x10)
022 U16 major_version // = 46 (0x2E)
023 U30 constant_int_pool_count
024 ConstantInteger[constant_int_pool_count] // Cpool entries for integers
025 U30 constant_uint_pool_count
026 ConstantUInteger[constant_uint_pool_count] // Cpool entries for uints
027 U30 constant_double_pool_count
028 ConstantDouble[constant_double_pool_count] // Cpool entries for doubles
029 U30 constant_string_pool_count
030 ConstantString[constant_string_pool_count] // Cpool entries for strings
031 U30 constant_namespace_pool_count
032 ConstantNamespace[constant_namespace_pool_count] // Cpool entries for namespaces
033 U30 constant_namespace_set_pool_count
034 ConstantNamespaceSet[constant_namespace_set_pool_count] // Cpool entries for namespace sets
035 U30 constant_multiname_pool_count
036 ConstantMultiname[constant_multiname_pool_count] // Cpool entries for Multinames, Qnames, RTQnames, and RTQnamesLate
037 U30 methods_count
038 MethodInfo[methods_count]
039 U30 metadata_count
040 MetadataInfo[metadata_count]
041 U30 class_count
042 InstanceInfo[class_count]
043 ClassInfo[class_count]
044 U30 script_count
045 ScriptInfo[script_count] // ScriptInfo[script_count-1] is main entry point
046 U30 bodies_count
047 MethodBody[bodies_count]
048 }
049
050
051 ConstantInteger {
052 S32 value
053 }
054
055 ConstantUInteger {
056 U32 value
057 }
058
059 ConstantDouble {
060 U64 doublebits (little endian)
061 }
062
063 ConstantString {
064 U30 length
065 U8[length] // UTF-8 encoded string
066 }
067
068 ConstantNamespace {
069 U8 kind
070 union {
071 kind=8,5,22,23,24,25,26 { // CONSTANT_Namespace,
// CONSTANT_PrivateNamespace,
// CONSTANT_PackageNamespace,
// CONSTANT_PacakgeInternalNamespace,
// CONSTANT_ProtectedNamespace,
// CONSTANT_ExplicitNamespace,
// CONSTANT_MultinameL
072 U30 name_index // CONSTANT_Utf8 uri (maybe 0)
073 }
074 }
075 }
076
077 ConstantNamespaceSet {
078 U30 namespace_count
079 U30[namespace_count] // CONSTANT_Namespace
080 }
081
082 ConstantMultiname {
083 U8 kind
084 union {
085 kind=7,13 { // CONSTANT_Qname + CONSTANT_QnameA
086 U30 namespace_index // CONSTANT_Namespace, 0=AnyNamespace wildcard
087 U30 name_index // CONSTANT_Utf8, 0=AnyName wildcard
088 }
089 kind=9,14 { // CONSTANT_Multiname, CONSTANT_MultinameA
090 U30 name_index // CONSTANT_Utf8 simple name. 0=AnyName wildcard
091 U30 namespace_set_index
092 }
093 kind=15,16 { // CONSTANT_RTQname + CONSTANT_RTQnameA
094 U30 name_index // CONSTANT_utf8, 0=AnyName wildcard
095 }
096 kind=27 { // CONSTANT_MultinameL
097 U30 namespace_set_index
}
098 kind=17,18 // CONSTANT_RTQnameL + CONSTANT_RTQnameLA
099 }
100 }
101
102 Traits {
103 U30 count
104 Trait[count] {
105 U30 name_index // CONSTANT_QName
106 U8 kind // hi 4 bits are flags, 0x04: (1=has_metadata, 0=no metadata)
107 union {
108 kind=0,6 { // slot, const
109 U30 slot_id // 0=autoassign
110 U30 type_index // CONSTANT_Multiname, 0=Object
111 U30 value_index // CONSTANT_<kind> or 0 for undefined - <kind> depends on the value of value_kind
112 U8 value_kind // cpool kind the value is, only present if value_index != 0
113 }
114 kind=1,2,3 { // method, getter, setter
115 U30 disp_id // 0=autoassign
116 U30 method_info // method must be parsed already
117 // attrs are stored in the hi 4 bits of the kind byte
118 // 0x01: (1=final,0=virtual), 0x02: (1=override,0=new)
119 }
120 kind=4 { // class
121 U30 slot_id // 0=autoassign
122 U30 class_info // class must have been parsed already
123 }
124 kind=5 { // function
125 U30 slot_index // 0=autoassign
126 U30 method_info // method_info of function residing in this slot
127 }
128 }
129 if ( (kind >> 4) & 0x04 ) // these are only present when the kind contains the has_metadata flag
130 {
131 U30 metadata_count // Number of metadata
132 U30 metadata[count] // MetadataInfo indices
133 }
134 }
135 }
136
137 MetadataInfo {
138 U30 name_index // CONSTANT_utf8
139 U30 values_count // # of values in this metadata
140 U30 keys[values_count] // CONSTANT_utf8, 0 = keyless
141 U30 values[values_count] // CONSTANT_utf8
142 }
143
144 InstanceInfo {
145 U30 name_index // CONSTANT_QName (definition)
146 U30 super_index // CONSTANT_Multiname (reference)
147 U8 flags // 1 = sealed, 0 = dynamic
148 // 2 = final
149 // 4 = interface
150 U30 protectedNS if flags & 8
151 U30 interfaces_count
152 U30 interfaces[interfaces_count] // CONSTANT_Multiname (references)
153 U30 iinit_index // MethodInfo
154 Traits instance_traits
155 }
156
157 ClassInfo {
158 U30 cinit_index // MethodInfo
159 Traits static_traits
160 }
161
162 ScriptInfo {
163 U30 init_index // MethodInfo
164 Traits traits
165 }
166
167 // A MethodInfo describes the method signature
168 MethodInfo {
169 U30 param_count
170 U30 ret_type // CONSTANT_Multiname, 0=any type (*)
171 U30 param_types[param_count] // CONSTANT_Multiname, 0=any type (*)
172 U30 name_index // 0=no name.
173 // 1=need_arguments, 2=need_activation, 4=need_rest 8=has_optional 16=ignore_rest, 32=explicit, 64=setsdxns, 128=has_paramnames
174 U8 flags
175 U30 optional_count // if has_optional
176 ValueKind[optional_count] // if has_optional
177 U30 param_names[param_count] // if has_paramnames
178 }
179
180 ValueKind {
181 U30 value_index // the index for the value in the cpool
182 U8 value_kind // the kind indicating which cpool the value is in
183 }
184
185 // A MethodBody describes the method implementation.
186 // not required for native methods or interface methods.
187 MethodBody {
188 U30 method_info
189 U30 max_stack
190 U30 max_regs
191 U30 scope_depth
192 U30 max_scope
193 U30 code_length
194 U8 code[code_length]
195 U30 ex_count
196 Exception[ex_count]
197 Traits traits // activation traits
198 }
199
200 Exception {
201 U30 start // Offsets of beginning and
202 U30 end // end of the try block
203 U30 target // Target PC to transfer control to (catch)
204 U30 type_index // Type matched by this exception handler
205 U30 name_index // Name of the exception variable
206 }
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