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diff --git a/tools/build/src/engine/command.h b/tools/build/src/engine/command.h
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+/*
+ * Copyright 1994 Christopher Seiwald.
+ *
+ * This file is part of Jam - see jam.c for Copyright information.
+ */
+
+/*
+ * command.h - the CMD structure and routines to manipulate them
+ *
+ * Both ACTION and CMD contain a rule, targets, and sources.  An
+ * ACTION describes a rule to be applied to the given targets and
+ * sources; a CMD is what actually gets executed by the shell.  The
+ * differences are due to:
+ *
+ *  ACTIONS must be combined if 'actions together' is given.
+ *  ACTIONS must be split if 'actions piecemeal' is given.
+ *  ACTIONS must have current sources omitted for 'actions updated'.
+ *
+ * The CMD datatype holds a single command that is to be executed
+ * against a target, and they can chain together to represent the
+ * full collection of commands used to update a target.
+ *
+ * Structures:
+ *
+ *  CMD - an action, ready to be formatted into a buffer and executed.
+ *
+ * External routines:
+ *
+ *  cmd_new() - return a new CMD or 0 if too many args.
+ *  cmd_free() - delete CMD and its parts.
+ *  cmd_next() - walk the CMD chain.
+ *  cmd_release_targets_and_shell() - CMD forgets about its targets & shell.
+ */
+
+
+/*
+ * CMD - an action, ready to be formatted into a buffer and executed.
+ */
+
+#ifndef COMMAND_SW20111118_H
+#define COMMAND_SW20111118_H
+
+#include "lists.h"
+#include "rules.h"
+#include "strings.h"
+
+
+typedef struct _cmd CMD;
+
+/*
+ * A list whose elements are either TARGETS or CMDS.
+ * CMDLIST is used only by CMD.  A TARGET means that
+ * the CMD is the last updating action required to
+ * build the target.  A CMD is the next CMD required
+ * to build the same target.  (Note that a single action
+ * can update more than one target, so the CMDs form
+ * a DAG, not a straight linear list.)
+ */
+typedef struct _cmdlist {
+    struct _cmdlist * next;
+    union {
+        CMD * cmd;
+        TARGET * t;
+    } impl;
+    char iscmd;
+} CMDLIST;
+
+CMDLIST * cmdlist_append_cmd( CMDLIST *, CMD * );
+CMDLIST * cmdlist_append_target( CMDLIST *, TARGET * );
+void cmd_list_free( CMDLIST * );
+
+struct _cmd
+{
+    CMDLIST * next;
+    RULE * rule;      /* rule->actions contains shell script */
+    LIST * shell;     /* $(JAMSHELL) value */
+    LOL    args;      /* LISTs for $(<), $(>) */
+    string buf[ 1 ];  /* actual commands */
+    int    noop;      /* no-op commands should be faked instead of executed */
+    int    asynccnt;  /* number of outstanding dependencies */
+    TARGETS * lock;   /* semaphores that are required by this cmd. */
+    TARGETS * unlock; /* semaphores that are released when this cmd finishes. */
+    char   status;    /* the command status */
+};
+
+CMD * cmd_new
+(
+    RULE * rule,     /* rule (referenced) */
+    LIST * targets,  /* $(<) (ownership transferred) */
+    LIST * sources,  /* $(>) (ownership transferred) */
+    LIST * shell     /* $(JAMSHELL) (ownership transferred) */
+);
+
+void cmd_release_targets_and_shell( CMD * );
+
+void cmd_free( CMD * );
+
+#define cmd_next( c ) ((c)->next)
+
+#endif