file format

[ksherlock]

Hi there,

The other day I was looking for information on SN Object files and this was the only information I found. This was very helpful and I was able to work out some more information (via the 65816 version of the SN assembler):

Record $1e: (created with /z): This sets the current file/line number.

Parameters:

• uint16_t file ID
• uint32_t line number

Record $22: (created with /z): This increments the current line number

Parameters:

• (none)

Record $24: (created with /z): This adjusts the current line number:

Parameters:

• uint8_t amount

Record $0a: Relocation record This consists of the header format you worked out and an expression tree:

Header:

• uint8_t type
• uint16_t address

type values:

• $32 - 1-byte, pc-relative
• $34 - 2-byte, pc-relative
• $02 - 1 byte
• $1a - 2 byte
• $2c - 3 byte
• $10 - 4 byte
• $0a - 1 byte (with truncation check?)
• $1c - 2 byte (with truncation check?)
• $30 - 3 byte (with truncation check?)

Expression tree:

This is an expression composed of 1 or more binary operators and terminals (constants, external symbols references, and internal section references). There is no explicit count or terminator but the length starts at 1, decrements every time a parameter is read, and increments by 2 whenever a binary operator is encountered.

operators:

• $20 =
• $22 <>
• $24 <=
• $26 <
• $28 >=
• $2a >
• $2c +
• $2e -
• $30 *
• $32 /
• $34 &
• $36 !
• $38 ^
• $3a <<
• $3c >>
• $3e %

terminals:

• 0x00 const (followed by uint32_t constant value)
• 0x02 external symbol reference (followed by uint16_t symbol id)
• 0x04 section reference (followed by uint16_t section id)

An expression like a+b*c+1 would create a tree like this:

    +
   / \
  1   +
     / \
    *   a
   / \
  c   b

which is encoded as: + 1 + * c b a (operator, left child, right child, recursively)

You could rebuild the tree to evaluate it or just process it backwards as RPN (a b c * + 1 +)

[Mr-Wiseguy]

Thanks! As it stands I ended up using a different solution for my project (a decompilation of an N64 game) that avoided needing to handle SN objects, but I'll be sure to share this info with some others who would be interested in knowing it.