Notes on StringIdMap (main class org.mozilla.javascript.tools.idswitch.StringIdMap) utility

The main purpose of this utility is to generate Java code to map strings to some ids that can be used, for example, in a switch statement.

The utility scans the file for lines with the following structure:

// #string_id_map#
... <DEFINITION AREA>
// #generated#
...<GENERATED AREA>
// #/generated#
... <DEFINITION AREA>
// #/string_id_map#

Then every line in <DEFINITION AREA> is scanned for the pattern:
^[ \t]*Id_([0-9a-zA-Z_]+)[ \t]*=.*$

Each such patterns adds a mapping form string $1 to Id_\$ or if the line also contains the pattern //\s*#string=\s*([^#]+)\s*#, then it adds map of $1 in this pattern to Id_\$

After that lines in <GENERATED AREA> are replaced by a code block that sets variable "id" to Id_<name> if variable "s" equals <name> (or value defined by //#string=...# construction in the line with Id_<name>) or 0 otherwise.
If the new code for <GENERATED AREA> is identical to old one, the file is not touched otherwise <GENERATED AREA> is overwritten by the new code and a time stamp is appended after #generated#.

For example, if file x.java contains:

// #string_id_map#

    private int getId(String s) {
        int id;
// #generated# Initial version
// #/generated#
        return id;
    }

    private static final int
        Id_x       = 1,
        Id_y       = 2,
        Id_hello   = 3, // #string = Hello, World! #
        Id_symbols = 4, // #string=<<*Symbols*>>#
        Id_nice    = 5,
        Id_for     = 6,
        Id_bar     = 7;

// #/string_id_map#

....

    private double getFieldValue(String s) {

// #string_id_map#
    final int
        Id_field1 = 1,
        Id_field2 = 2,
        Id_field3 = 3,
        Id_one_more_field = 4; // #string = ONE%MORE%FIELD#

        int id;
// #generated# Initial version
// #/generated#
// #/string_id_map#
        switch (id) {
            case Id_field1: return field1;
            case Id_field2: return field2;
            case Id_field3: return field3;
            case Id_one_more_field: return one_more_field;
        }
        throw new RuntimeException("No such field");
    }


then invocation
java org.mozilla.javascript.tools.string_switch.StringIdMap x.java
would replace that by a code fragment similar to:

// #string_id_map#

    private int getId(String s) {
        int id;
// #generated# Last update: 2001-05-25 18:00:24 GMT+02:00
        L0: { id = 0; String X = null; int c;
            L: switch (s.length()) {
            case 1: c=s.charAt(0);
                if (c=='x') { id=Id_x; break L0; }
                else if (c=='y') { id=Id_y; break L0; }
                break L;
            case 3: c=s.charAt(0);
                if (c=='b') { if (s.charAt(2)=='r' && s.charAt(1)=='a') {id=Id_bar; break L0;} }
                else if (c=='f') { if (s.charAt(2)=='r' && s.charAt(1)=='o') {id=Id_for; break L0;} }
                break L;
            case 4: X="nice";id=Id_nice; break L;
            case 13: c=s.charAt(0);
                if (c=='<') { X="<<*Symbols*>>";id=Id_symbols; }
                else if (c=='H') { X="Hello, World!";id=Id_hello; }
                break L;
            }
            if (X!=null && X!=s && !X.equals(s)) id = 0;
        }
// #/generated#
        return id;
    }

    private static final int
        Id_x       = 1,
        Id_y       = 2,
        Id_hello   = 3, // #string = Hello, World! #
        Id_symbols = 4, // #string=<<*Symbols*>>#
        Id_nice    = 5,
        Id_for     = 6,
        Id_bar     = 7;

// #/string_id_map#

....

    private double getFieldValue(String s) {

// #string_id_map#
    final int
        Id_field1 = 1,
        Id_field2 = 2,
        Id_field3 = 3,
        Id_one_more_field = 4; // #string = ONE%MORE%FIELD#

        int id;
// #generated# Last update: 2001-05-25 16:48:50 GMT+02:00
        L0: { id = 0; String X = null; int c;
            int s_length = s.length();
            if (s_length==6) {
                c=s.charAt(5);
                if (c=='1') { X="field1";id=Id_field1; }
                else if (c=='2') { X="field2";id=Id_field2; }
                else if (c=='3') { X="field3";id=Id_field3; }
            }
            else if (s_length==14) { X="ONE%MORE%FIELD";id=Id_one_more_field; }
            if (X!=null && X!=s && !X.equals(s)) id = 0;
        }
// #/generated#
// #/string_id_map#
        switch (id) {
            case Id_field1: return field1;
            case Id_field2: return field2;
            case Id_field3: return field3;
            case Id_one_more_field: return one_more_field;
        }
        throw new RuntimeException("No such field");
    }
