aw/laymanshex
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added factor to variable bit size -> easier offset scripting

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This commit is contained in:
gutmet 2020-04-30 16:08:10 +02:00
parent 55bf95a397
commit ba5f048a92
2 changed files with 18 additions and 5 deletions
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4
README
View File

@ -30,7 +30,7 @@ type = bytefield
| "float32" | "float64"
.
bytefield = "byte[" ( INTEGER | IDENT ) "]".
bytefield = "byte[" ( INTEGER | IDENT [ "*" INTEGER ]) "]".
```
The identifier of a definition line can be left empty to ignore that particular value.
@ -59,7 +59,7 @@ element of the sequence at a certain offset:
```
little endian
: byte[offset]
: byte[offset*32]
value : int32
```

19
laymanshex.go
View File

@ -168,17 +168,30 @@ type formatAssignment struct {
used bool
}
func splitVariableExpression(s string) (string, int64) {
split := strings.Split(s, "*")
name := trim(split[0])
if len(split) == 2 {
factor, err := strconv.ParseInt(split[1], 0, 64)
optPanic("parsing definition: "+s, err)
return name, factor
}
return name, 1
}
func (part *filePart) setByteFieldHandling(assignments map[string]*formatAssignment) {
tmp := trim(strings.TrimSuffix(strings.TrimPrefix(part.parttype, "byte["), "]"))
var bytes int64
var err error
if bytes, err = strconv.ParseInt(tmp, 10, 64); err != nil {
if ass, ok := assignments[tmp]; ok {
bytes = ass.val
variable, factor := splitVariableExpression(tmp)
if ass, ok := assignments[variable]; ok {
bytes = ass.val * factor
ass.used = true
err = nil
} else {
msg := "byte field definition in format description: could neither parse size to int64 nor obtain value from -fvar"
msg := "byte field definition in format description: could neither parse size to int64 nor obtain value from -fvar" +
" (" + part.parttype + ")"
if part.name != "" {
msg += " - definition of " + part.name
}