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Comprehensive technical documentation covering: - Hardware: OCS/ECS/AGA custom chip registers, Copper & Blitter deep dives - Boot sequence: cold boot through startup-sequence - Binary format: HUNK executable spec, relocation, debug info - Linking & ABI: .fd files, LVO tables, register calling conventions - Exec kernel: tasks, interrupts, memory, signals, semaphores - AmigaDOS: file I/O, FFS/OFS layout, CLI/Shell scripting - Graphics: planar bitmaps, Copper programming, HAM/EHB modes - Intuition: screens, windows, IDCMP, BOOPSI - Devices: trackdisk, SCSI, serial, timer, audio, keyboard - Libraries: utility, expansion, IFFParse, locale, ARexx - Networking: bsdsocket API, SANA-II, TCP/IP stack comparison - Toolchain: GCC, vasm/vlink, SAS/C, NDK, debugging - Reverse engineering: IDA/Ghidra setup, compiler fingerprints, case studies - CPU & MMU: 68040/060 emulation libs, PMMU, cache management - Driver development: SANA-II, Picasso96/RTG, AHI audio All files include breadcrumb navigation. No local paths or proprietary content.
158 lines
4 KiB
Markdown
158 lines
4 KiB
Markdown
[← Home](../README.md) · [Exec Kernel](README.md)
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# Lists and Nodes — MinList, List, Node, MinNode
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## Overview
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AmigaOS uses **intrusive doubly-linked lists** throughout exec: the task list, library list, device list, memory list, port list, and more all use the same `List`/`Node` structures defined in `exec/lists.h`.
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---
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## Structures
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```c
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/* exec/nodes.h — NDK39 */
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struct Node {
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struct Node *ln_Succ; /* pointer to next node (NULL at tail sentinel) */
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struct Node *ln_Pred; /* pointer to prev node (NULL at head sentinel) */
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UBYTE ln_Type; /* node type — NT_TASK, NT_LIBRARY, NT_MEMORY... */
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BYTE ln_Pri; /* scheduling priority (used by Enqueue) */
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char *ln_Name; /* optional name string (NULL = anonymous) */
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};
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struct MinNode {
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struct MinNode *mln_Succ;
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struct MinNode *mln_Pred;
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/* no type, priority, or name — minimal overhead */
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};
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```
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```c
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/* exec/lists.h — NDK39 */
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struct List {
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struct Node *lh_Head; /* first node (or tail sentinel if empty) */
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struct Node *lh_Tail; /* always NULL — marks end of list */
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struct Node *lh_TailPred; /* last node (or head sentinel if empty) */
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UBYTE lh_Type; /* list type */
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UBYTE lh_pad;
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};
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struct MinList {
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struct MinNode *mlh_Head;
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struct MinNode *mlh_Tail; /* always NULL */
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struct MinNode *mlh_TailPred;
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};
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```
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### Node Type Constants
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```c
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/* exec/nodes.h */
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#define NT_UNKNOWN 0
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#define NT_TASK 1 /* exec Task */
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#define NT_INTERRUPT 2 /* Interrupt server */
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#define NT_DEVICE 3 /* Device */
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#define NT_MSGPORT 4 /* MsgPort */
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#define NT_MESSAGE 5 /* Message */
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#define NT_FREEMSG 6
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#define NT_REPLYMSG 7
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#define NT_RESOURCE 8
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#define NT_LIBRARY 9 /* Library */
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#define NT_MEMORY 10 /* MemHeader */
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#define NT_SOFTINT 11
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#define NT_FONT 12
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#define NT_PROCESS 13 /* dos.library Process */
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#define NT_SEMAPHORE 14
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#define NT_SIGNALSEM 15 /* SignalSemaphore */
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#define NT_BOOTNODE 16
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#define NT_KICKMEM 17
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#define NT_GRAPHICS 18
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#define NT_DEATHMESSAGE 19
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```
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---
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## Initialising a List
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```c
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/* Stack-allocated list: */
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struct List myList;
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NewList(&myList); /* sets up sentinel pointers — mandatory */
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/* Or use NEWLIST() macro: */
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NEWLIST(&myList);
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```
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---
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## Adding and Removing Nodes
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```c
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/* Add at head (highest LRU position): */
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AddHead(&myList, &myNode); /* LVO -240 */
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/* Add at tail: */
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AddTail(&myList, &myNode); /* LVO -246 */
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/* Remove from wherever it is (no list pointer needed): */
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Remove(&myNode); /* LVO -252 */
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/* Priority-ordered insert (by ln_Pri, high first): */
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Enqueue(&myList, &myNode); /* LVO -270 */
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```
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---
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## Walking a List
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```c
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struct Node *node, *next;
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for (node = myList.lh_Head; node->ln_Succ != NULL; node = node->ln_Succ) {
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/* process node */
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}
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```
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Safe removal while iterating (save next before removing):
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```c
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for (node = myList.lh_Head; (next = node->ln_Succ) != NULL; node = next) {
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if (should_remove(node)) Remove(node);
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}
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```
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---
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## Finding a Node by Name
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```c
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struct Node *found = FindName(&SysBase->LibList, "dos.library");
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/* Returns NULL if not found */
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/* Always call under Forbid() if the list may change */
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```
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---
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## How the Sentinel Works
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The AmigaOS list design uses a **3-pointer layout** that avoids special-casing empty lists and end-of-list checks:
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```
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lh_Head ──→ [ Node A ]──→ [ Node B ]──→ [ tail sentinel ]
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lh_Tail = NULL (always)
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lh_TailPred ──────────────────────────→ [ Node B ]
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Empty list:
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lh_Head ──→ [ tail sentinel ]
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lh_TailPred ──→ [ head sentinel ]
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```
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Walking stops when `ln_Succ == NULL` — that is the tail sentinel's `lh_Tail` field.
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---
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## References
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- NDK39: `exec/nodes.h`, `exec/lists.h`
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- ADCD 2.1: `AddHead`, `AddTail`, `Remove`, `Enqueue`, `FindName`, `NewList`
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- *Amiga ROM Kernel Reference Manual: Exec* — lists chapter
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