Chunk - Revision history

Chekwob: 8 revisions imported: Initial import from Wikia

2019-04-27T17:44:32Z

8 revisions imported: Initial import from Wikia

Wikia>Chekwob: Add the checksum algorithm

2017-12-29T02:32:14Z

Add the checksum algorithm

Wikia>Warenhuis: Adding categories

2016-08-08T13:25:13Z

Adding categories

163.158.241.64: End of last Entry

2016-07-02T16:08:26Z

End of last Entry

Wikia>Thaswordster: Avoiding possible future confusion.

2015-07-30T01:16:57Z

Avoiding possible future confusion.

Wikia>WurlyFox: /* Types */

2015-07-25T23:30:47Z

‎Types

Wikia>WurlyFox: /* Format */

2015-07-25T23:20:41Z

‎Format

Wikia>WurlyFox: /* Chunk IDs/CIDs */

2015-07-25T23:14:10Z

‎Chunk IDs/CIDs

Wikia>WurlyFox: Created page with "Chunks are the highest level data containers in NSF files. Each chunk is 64kb (0x10000 bytes) in size, in congruence with the 64kb pages allocated to contain them. == Format ..."

2015-07-25T11:23:41Z

Created page with "Chunks are the highest level data containers in NSF files. Each chunk is 64kb (0x10000 bytes) in size, in congruence with the 64kb pages allocated to contain them. == Format ..."

New page

Chunks are the highest level data containers in NSF files. Each chunk is 64kb (0x10000 bytes) in size, in congruence with the 64kb pages allocated to contain them.

== Format ==

=== Uncompressed chunks ===

==== Non-texture chunks ====
{| class="article-table"
!Offset
!Field
!Size
!Value
|-
|0x0
|Magic Number
|2 bytes
|0x1234
|-
|0x2
|Type
|2 bytes
|!=1
|-
|0x4
|ID
|4 bytes
|*
|-
|0x8
|Entry Count
|4 bytes
|c
|-
|0xC
|Checksum
|4 bytes
|*
|-
|0x10
|Entry Offsets
|4 x c bytes
|*
|-
|0x10 + (4 x c)
|Entries
|* x c bytes
|*
|}

==== Texture chunks ====
{| class="article-table"
!Offset
!Field
!Size
!Value
|-
|0x0
|Magic Number
|2 bytes
|0x1234
|-
|0x2
|Type
|2 bytes
|1
|-
|0x4
|Texture Page EID
|4 bytes
|*
|-
|0x8
|Tex. Page Entry Type
|4 bytes
|5
|-
|0xC
|Checksum
|4 bytes
|*
|-
|0x10
|Texture data
|0xFFF0/65520 bytes
|*
|}

=== Compressed chunks ===
{| class="article-table"
!Offset
!Field
!Size
!Value
|-
|0x0
|Magic Number
|2 bytes
|0x1235
|-
|0x2
|Unused
|2 bytes
|*
|-
|0x4
|Length
|4 bytes
|l
|-
|0x8
|Skip
|4 bytes
|s
|-
|0xC
|Compressed data
|n bytes
|*
|-
|0xC+n
|Skipped data
|s bytes
|*
|-
|0xC+n+s
|Uncompressed data
|(0x10000 - l) bytes
|*
|}

== Types ==
{| class="article-table"
!Type
!Name
|-
|0
|Normal Chunk
|-
|1
|Texture Chunk
|-
|2
|Prototype Sound Chunk
|-
|3
|Sound Chunk
|-
|4
|Wavebank Chunk
|-
|5
|Speech Chunk
|}

== Chunk IDs/CIDs ==
Each chunk also has its own unique ID: chunk IDs have been assigned according to their sequence in the NSF file; the formula for a Chunk ID (referred to throughout this guide as CID) is: '(index << 1) - 1' or the sequence of odd numbers (which have have their LSB set). The reason for this will be explained shortly. **Texture chunks do NOT have their associated precomputed Chunk ID in the CID field-it is to be computed later.

← Older revision		Revision as of 02:32, 29 December 2017
Line 210:		Line 210:
	Texture chunks do not have a CID field with precomputed value. The texture paging routines manually compute CIDs for texture chunks.		Texture chunks do not have a CID field with precomputed value. The texture paging routines manually compute CIDs for texture chunks.
	[[Category:Structure]]		[[Category:Structure]]
		+
		+	== Checksums ==
		+	Each chunk includes a 32-bit checksum which can be used to verify the integrity of the chunk data. At least some PAL versions of the games enforce these checksums.
		+
		+	The checksum is computed as follows:
		+
		+	# Start with the value <code>0x12345678</code>.
		+	# For each byte of the 64K chunk:
		+	#* Add that byte to the current value. For the bytes from the checksum field itself (bytes 12 through 15), consider their value to be zero.
		+	#* Circularly left-shift the current value by three bits.
		+	# The final value is the correct checksum.
		+
		+	This procedure is also described by this C function:
		+
		+	<syntaxhighlight lang="cpp">
		+	uint32_t nsfChecksum(const unsigned char *data)
		+	{
		+	uint32_t checksum = 0x12345678;
		+	for (int i = 0;i < 65536;i++) {
		+	if (i < 12 \|\| i >= 16)
		+	checksum += data[i];
		+	checksum = checksum << 3 \| checksum >> 29;
		+	}
		+	return checksum;
		+	}
		+	</syntaxhighlight>

← Older revision		Revision as of 13:25, 8 August 2016
Line 209:		Line 209:

	Texture chunks do not have a CID field with precomputed value. The texture paging routines manually compute CIDs for texture chunks.		Texture chunks do not have a CID field with precomputed value. The texture paging routines manually compute CIDs for texture chunks.
		+	[[Category:Structure]]

← Older revision		Revision as of 01:16, 30 July 2015
Line 1:		Line 1:
−	Chunks are the highest level data containers in NSF files. Each chunk is ~~64kb~~ (0x10000 bytes) in size, in congruence with the ~~64kb~~ pages allocated to contain them.	+	Chunks (a.k.a. pages) are the highest level data containers in NSF files. Each chunk is 64KB (0x10000 bytes) in size, in congruence with the 64KB pages allocated to contain them.

	== Format ==		== Format ==

← Older revision		Revision as of 23:14, 25 July 2015
Line 154:		Line 154:

	== Chunk IDs/CIDs ==		== Chunk IDs/CIDs ==
−	Each chunk ~~also~~ has ~~its own~~ unique ID: chunk ~~IDs have~~ been assigned according to ~~their sequence~~ in the NSF file~~; the~~ formula for a ~~Chunk~~ ID ~~(referred to throughout this guide as~~ CID) is: '(index << 1) - 1' or the ~~sequence~~ of ~~odd numbers (which have have their~~ LSB ~~set)~~. ~~The reason for this will be explained shortly~~. **Texture chunks do ~~NOT~~ have ~~their associated precomputed Chunk ID in the~~ CID field~~-it is to be computed later~~.	+	Each chunk has a unique ID. A chunk ID has been assigned to each chunk according to its index in the NSF file. The formula for a chunk ID, or CID, is: '(index << 1) - 1', where chunk indices start at 1. This is equivalent to '(index << 1) \| 1' when chunks are zero-indexed. Thus, a chunk's index is contained in the leftmost 31 bits of its CID. The rightmost bit or LSB in a CID is an indicator bit or tag, and is always 1. A CID is typically stored in a tagged union with its replacement entry pointer as the key in an entry hash table slot. Its replacement pointer locates an entry contained in the chunk with that CID.
		+
		+	Texture chunks do not have a CID field with precomputed value. The texture paging routines manually compute CIDs for texture chunks.

← Older revision	Revision as of 17:44, 27 April 2019
(No difference)

@@ Line 43: / Line 43: @@
 |-
 |0x10 + (4 x c)
 |Entries
 |* x c bytes

@@ Line 193: / Line 193: @@
 |Speech Chunk
 |}
 == Chunk IDs/CIDs ==

@@ Line 129: / Line 129: @@
 |}
 == Types ==
 {| class="article-table"