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Diffstat (limited to 'twasm/README.md')
| -rw-r--r-- | twasm/README.md | 85 |
1 files changed, 73 insertions, 12 deletions
diff --git a/twasm/README.md b/twasm/README.md index d6d2ec5..c2cc263 100644 --- a/twasm/README.md +++ b/twasm/README.md @@ -12,6 +12,70 @@ I want to compile Bootler and Twasm with the Twasm assembler - [opcodes,ModR/M,SIB](http://ref.x86asm.net/coder64.html) (no secure site available) - [calling conventions](https://wiki.osdev.org/Calling_Conventions); I try to use System V +### tokeniser + +whitespace is ignored for the sake of readability; it can go between pretty much anything + +``` +------------------------ +tokeniser +------------------------ +byte(s) -> next byte(s) +------------------------ +Newline -> Newline + -> Komment + -> Operator + -> Directive + +Komment -> Newline + +Operator -> Newline + -> Komment + -> Operand + +Operand -> Newline + -> Komment + -> Comma + +Comma -> Operand + +Directive -> Newline + -> Komment + -> Operator +------------------------ +``` + +not yet implemented: + +``` +------------------------ +operand parser +------------------------ +byte(s) -> next byte(s) +------------------------ +START -> '[' + -> Register + -> Constant + +'[' -> Register + -> Constant + +']' -> END + +Register -> IF #[, ']' + -> Operator + +Constant -> IF #[, ']' + -> Operator + +Operator -> IF NOT #R, Register + -> Constant +------------------------ +:R: = whether a register has been found +:[: = whether a '[' has been found +------------------------ +``` + ### memory map ``` @@ -50,15 +114,15 @@ each token gets loaded into the token table with the following form: ### internal data structures -#### `tokens.by_nameX` +#### `tokens.[operators|registers]` -contains all tokens of that length followed by their ID. For some non-empty `tokens.by_nameX`, it is true that `tokens.by_name<X+1> - tokens.by_nameX` is the size in bytes of `tokens.by_nameX`. +contains tokens by their type. Intended to be searched by token name to get the token's ID. each entry is in the following form: ``` +----------+--------------------------------+ -|[2 bytes] | 8 * token_length - 1 0 | +| 47 32 | 31 0 | +----------+--------------------------------+ | token ID | string without null terminator | +----------+--------------------------------+ @@ -68,19 +132,16 @@ each entry is in the following form: example implementation: ```nasm -tokens: - .by_name1: - db "+" - dw 0x0062 - db "-" - dw 0x0063 - .by_name2: - db "r8" +tokens + .registers: + dd "r8" dw 0x0008 .by_name3: ; this is required for futureproofness; the caller can use this to - ; find the size of tokens.by_name2 + ; find the size of registers.by_name2 ``` +note that tokens longer than 4 bytes are problematic :/ + #### `tokens.by_id` contains some tokens with their metadata. Some tokens have embedded information (`0x10XX` for instance). Those will not have entries in this table, being handled instead inside the assemble function itself. |