beam_lib
provides an interface to files
created by the BEAM compiler ("BEAM files"). The format used,
a variant of "EA IFF 1985" Standard for Interchange Format Files,
divides data into chunks.
Chunk data can be returned as binaries or as compound terms.
Compound terms are returned when chunks are referenced by names
(atoms) rather than identifiers (strings). The names recognized
and the corresponding identifiers are abstract_code
("Abst"), attributes
("Attr"), exports
("ExpT"),
labeled_exports
("ExpT"), imports
("ImpT"),
locals
("LocT"), labeled_locals
("LocT"), and
atoms
("Atom").
The syntax of the compound term (ChunkData
) is as follows:
ChunkData = {ChunkId, binary()}
| {abstract_code, AbstractCode}
| {attributes, [{Attribute, [AttributeValue]}]}
| {exports, [{Function, Arity}]}
| {labeled_exports, [{Function, Arity, Label}]}
| {imports, [{Module, Function, Arity}]}
| {locals, [{Function, Arity}]}]}
| {labeled_locals, [{Function, Arity, Label}]}]}
| {atoms, [{integer(), atom()}]}
ChunkRef = ChunkId | ChunkName
ChunkName = abstract_code | attributes | exports
| labeled_exports | imports | locals | labeled_locals
| atoms
ChunkId = string()
AbstractCode = {AbstVersion, forms()}
| no_abstract_code
AbstVersion = atom()
Attribute = atom()
AttributeValue = term()
Module = Function = atom()
Arity = integer() >= 0
Label = integer() >= 0
The list of attributes is sorted on Attribute
, and
each attribute name occurs once in the list. The attribute
values occur in the same order as on the file. The lists of
functions are also sorted. It is not checked that the forms
conform to the abstract format indicated by AbstVersion
.
no_abstract_code
means that the "Abst" chunk is present,
but empty.
Each of the functions described below accept either a filename or a binary containing a beam module.
chunks(FileNameOrBinary, [ChunkRef]) ->
{ok, {Module, [ChunkData]}} | {error, Module, Reason}
Types:
FileNameOrBinary = string() | atom() | binary()
Reason = {unknown_chunk, FileName, atom()}
| - see info/1 -
The chunks/2
function reads chunk data for selected
chunks. The order of the returned list of chunk data is determined
by the order of the list of chunks references; if each
chunk data were replaced by the tag, the result would be the
given list.
version(FileNameOrBinary) ->
{ok, {Module, Version}} | {error, Module, Reason}
Types:
FileNameOrBinary = string() | atom() | binary()
Version = [term()]
Reason = - see chunks/2 -
The version/1
function returns the module version(s)
found in a BEAM file.
Types:
FileName = string() | atom()
FileNameOrBinary = FileName | binary()
SourceRef = {file, FileName} | {binary, binary()}
ChunkInfo = {ChunkId, StartPosition, Size}
StartPosition = integer() > 0
Size = integer() >= 0
Reason = {chunk_too_big, FileName, ChunkId, ChunkSize, FileSize}
| {invalid_beam_file, FileName, FilePosition}
| {invalid_chunk, FileName, ChunkId}
| {missing_chunk, FileName, ChunkId}
| {not_a_beam_file, FileName}
| {file_error, FileName, FileError}
The info/1
function extracts some information about
a BEAM file: the file name, the module name, and
for each chunk the identifier as well as the position and size
in bytes of the chunk data.
cmp(FileNameOrBinary, FileNameOrBinary) ->
ok | {error, Module, Reason}
Types:
FileName = string() | atom()
FileNameOrBinary = FileName | binary()
Reason = {modules_different, Module, Module}
| {chunks_different, ChunkId}
| - see info/1 -
The cmp/2
function compares the contents of two BEAM
files. If the module names are the same, and the chunks with
the identifiers "Code", "ExpT", "ImpT", "StrT", and "Atom"
have the same contents in both files, ok
is
returned. Otherwise an error message is returned.
cmp_dirs(Directory1, Directory2) ->
{Only1, Only2, Different} | {error, Module, Reason}
Types:
Directory1 = Directory2 = string() | atom()
Different = [{FileName1, FileName2}]
Only1 = Only2 = [FileName]
FileName = FileName1 = FileName2 = string()
Reason = - see info/1 -
The cmp_dirs/2
function compares the BEAM files in
two directories. Only files with extension ".beam" are
compared. BEAM files that exist in directory
Directory1
(Directory2
) only are returned in
Only1
(Only2
). BEAM files that exist on both
directories but are considered different by cmp/2
are
returned as pairs {FileName1
, FileName2
} where
FileName1
(FileName2
) exists in directory
Directory1
(Directory2
).
diff_dirs(Directory1, Directory2) ->
ok | {error, Module, Reason}
Types:
Directory1 = Directory2 = string() | atom()
Reason = - see info/1 -
The diff_dirs/2
function compares the BEAM files in
two directories the way cmp_dirs/2
does, but names of
files that exist in only one directory or are different are
presented on standard output.
strip(FileNameOrBinary) ->
{ok, {Module, FileNameOrBinary}} | {error, Module, Reason}
Types:
FileName = string() | atom()
FileNameOrBinary = FileName | binary()
Reason = - see info/1 -
The strip/1
function removes all chunks from a BEAM
file except those needed by the loader. In particular, the
abstract code is removed. The module name found in the file
and the file name, possibly with the ".beam" extension
added, are returned.
strip_files(Files) ->
{ok, [{Module, FileNameOrBinary]}} | {error, Module, Reason}
Types:
Files = [FileNameOrBinary]
FileName = string() | atom()
FileNameOrBinary = FileName | binary()
Reason = - see info/1 -
The strip_files/1
function removes all chunks except
those needed by the loader from BEAM files. In particular,
the abstract code is removed. The returned list contains one
element for each given file name, ordered as the given
list. The list element is a pair of the module name found in
the file and the file name, the latter possibly with the
".beam" extension added.
strip_release(Directory) ->
{ok, [{Module, FileName]}} | {error, Module, Reason}
Types:
Directory = string() | atom()
FileName = string()
Reason = - see info/1 -
The strip_release/1
function removes all chunks
except those needed by the loader from the BEAM files of a
release. Directory
should be the installation root
directory. For example, the current OTP release can be
stripped with the call
beam_lib:strip_release(code:root_dir())
. The returned
list contains module names and file names of stripped files.
format_error(Error) -> character_list()
Given the error returned by any function in this module,
the function format_error
returns a descriptive string
of the error in English. For file errors, the function
format_error/1
in the file
module is called.