Refactor header configuration handling.

- Mark optional fields and normalize them on load.
- Validate (work in progress) required fields and their values.
- Make sure that errors point to useful location in the config file.

1 files changed, 47 insertions, 13 deletions

diff --git a/elf/header.lua b/elf/header.lua
index 6baf327..b289f13 100644
--- a/elf/header.lua
+++ b/elf/header.lua
@@ -1,29 +1,63 @@
 local fmt = require("elf.fmt")
+local ec = require("elf.constants")
 
 ---@alias Magic [integer, integer, integer, integer]
 
 ---@class Header
----@field magic Magic
+---@field magic? Magic
 ---@field class Class
 ---@field data Endian
----@field ident_version integer
----@field osabi Osabi
----@field abiversion integer
+---@field ident_version? integer
+---@field osabi? Osabi
+---@field abiversion? integer
 ---@field type Type
 ---@field machine Machine
----@field version integer
----@field entry integer
----@field phoff integer
----@field shoff integer
----@field flags integer
----@field ehsize integer
+---@field version? integer
+---@field entry? integer
+---@field phoff? integer
+---@field shoff? integer
+---@field flags? integer
+---@field ehsize? integer
 ---@field phentsize? integer
 ---@field phnum? integer
----@field shentsize integer
----@field shnum integer
----@field shstrndx integer
+---@field shentsize? integer
+---@field shnum? integer
+---@field shstrndx? integer
 local M = {}
 
+function M.normalize(hdr)
+    hdr.magic = hdr.magic or { 0x7f, 0x45, 0x4c, 0x46 }
+    hdr.ident_version = hdr.ident_version or ec.VERSION
+    hdr.osabi = hdr.osabi or ec.Osabi.sysv
+    hdr.abiversion = hdr.abiversion or 0
+    hdr.version = hdr.version or ec.VERSION
+    hdr.entry = hdr.entry or 0
+    hdr.phoff = hdr.phoff or 0
+    hdr.shoff = hdr.shoff or 0
+    hdr.flags = hdr.flags or 0
+    hdr.ehsize = hdr.ehsize or 0
+    hdr.phentsize = hdr.phentsize or 0
+    hdr.phnum = hdr.phnum or 0
+    hdr.shentsize = hdr.shentsize or 0
+    hdr.shnum = hdr.shnum or 0
+    hdr.shstrndx = hdr.shstrndx or 0
+end
+
+function M.validate(hdr)
+    if not hdr.class then error("class is required in header", 3) end
+    if not hdr.data then error("data is required in header", 3) end
+    if not hdr.type then error("type is required in header", 3) end
+    if not hdr.machine then error("machine is required in header", 3) end
+
+    if hdr.class ~= ec.Class.bit32 and hdr.class ~= ec.Class.bit64 then
+        error("class must be Class.bit32 or Class.bit64 in header", 3)
+    end
+    if hdr.data ~= ec.Endian.little and hdr.data ~= ec.Endian.big then
+        error("data must be Endian.little or Endian.big in header", 3)
+    end
+    -- TODO additional validations
+end
+
 ---@param hdr Header
 ---@return string
 ---@nodiscard