From Erlang Community

Revision as of 20:19, 19 August 2009 (edit) Zghst (Talk | contribs) ← Previous diff		Revision as of 20:40, 19 January 2011 (edit) (undo) Zghst (Talk | contribs) Next diff →
Line 12:		Line 12:
	== Types ==		== Types ==
-	Most used types are: Sint, Uint, Eterm, ...	+	See sys.h for the basic datatypes:
-	Conversion is done in erts/emulator/beam/big.c. For example uint_to_big(Uint x, Eterm *y). term_to_Uint(Eterm term, Uint *up)	+	** Data types:
		+	**
		+	** Eterm: A tagged erlang term (possibly 64 bits)
		+	** BeamInstr: A beam code instruction unit, possibly larger than Eterm, not smaller.
		+	** UInt: An unsigned integer exactly as large as an Eterm.
		+	** SInt: A signed integer exactly as large as an eterm and therefor large
		+	** enough to hold the return value of the signed_val() macro.
		+	** UWord: An unsigned integer at least as large as a void * and also as large
		+	** or larger than an Eterm
		+	** SWord: A signed integer at least as large as a void * and also as large
		+	** or larger than an Eterm
		+	** Uint32: An unsigned integer of 32 bits exactly
		+	** Sint32: A signed integer of 32 bits exactly
		+	** Uint16: An unsigned integer of 16 bits exactly
		+	** Sint16: A signed integer of 16 bits exactly.
		+
		+	See erts/emulator/beam/big.c for the conversion between types. For example uint_to_big(Uint x, Eterm *y). term_to_Uint(Eterm term, Uint *up).
		+	An Eterm can contain any erlang term like atoms, integers, etc.
		+
		+	== BIFs ==
		+
		+	The bifs are summed up in the bif.tab file. For example:
		+	bif 'erl.lang':exit/1 ebif_exit_1
		+	bif erlang:exit/2
		+
		+	This means the exit bif is mapped to the exit_1 method in the bif.c file.
		+	The bif.c file holds the bif implementations like:
		+
		+	BIF_RETTYPE spawn_3(BIF_ALIST_3)
		+	{...
		+	BIF_ALIST_3 means you have BIF_P, BIF_ARG1 to 3 and
		+	The arguments BIF_ARG1 are Eterms, so you have to check them with is_number(BIF_ARG_1), is_atom, is_tuple, etc
		+
		+
		+
		+
		+
		+
	== Scheduler ==		== Scheduler ==

---

Revision as of 20:40, 19 January 2011

A guide to the erlang source.

Contents 1 Download 2 Tree 3 Atoms 4 Types 5 BIFs 6 Scheduler 7 Process 8 Monitors and links

Download

The source can be downloaded from: http://erlang.org/download.html or http://github.com/mfoemmel/erlang-otp/tree/master

Tree

Most of the interesting code is in: erts/emulator/beam

Atoms

The atoms used in erlang are listed in erts/emulator/beam/atom.names and are referenced in the code as am_foo. So the 'EXIT' atom is am_EXIT in the code.

Types

See sys.h for the basic datatypes:

• • Data types:
  • Eterm: A tagged erlang term (possibly 64 bits)
  • BeamInstr: A beam code instruction unit, possibly larger than Eterm, not smaller.
  • UInt: An unsigned integer exactly as large as an Eterm.
  • SInt: A signed integer exactly as large as an eterm and therefor large
  • enough to hold the return value of the signed_val() macro.
  • UWord: An unsigned integer at least as large as a void * and also as large
  • or larger than an Eterm
  • SWord: A signed integer at least as large as a void * and also as large
  • or larger than an Eterm
  • Uint32: An unsigned integer of 32 bits exactly
  • Sint32: A signed integer of 32 bits exactly
  • Uint16: An unsigned integer of 16 bits exactly
  • Sint16: A signed integer of 16 bits exactly.

See erts/emulator/beam/big.c for the conversion between types. For example uint_to_big(Uint x, Eterm *y). term_to_Uint(Eterm term, Uint *up). An Eterm can contain any erlang term like atoms, integers, etc.

BIFs

The bifs are summed up in the bif.tab file. For example: bif 'erl.lang':exit/1 ebif_exit_1 bif erlang:exit/2

This means the exit bif is mapped to the exit_1 method in the bif.c file. The bif.c file holds the bif implementations like:

BIF_RETTYPE spawn_3(BIF_ALIST_3) {... BIF_ALIST_3 means you have BIF_P, BIF_ARG1 to 3 and The arguments BIF_ARG1 are Eterms, so you have to check them with is_number(BIF_ARG_1), is_atom, is_tuple, etc

Scheduler

The process struct is defined in erts/emulator/beam/process.h. The important function is Process *schedule(Process *p, int calls) in process.c . The next process is picked in "pick_next_process" of that method.

Process

Process statuses are:

1. define P_FREE 0
2. define P_RUNABLE 1
3. define P_WAITING 2
4. define P_RUNNING 3
5. define P_EXITING 4
6. define P_GARBING 5
7. define P_SUSPENDED 6

Monitors and links

See erl_monitor.c and .h. The main structs are ErtsLinks and ErtsMonitor. Each process has a *ErtLinks and *ErtsMonitor (herein all its links/monitors are kept as an AVL tree). Actions are done with erts_sweep_links(ErtsLink *root, ...) and erts_sweep_monitors(ErtsMonitor *root, ...).