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https://github.com/alfishe/amiga-bootcamp.git
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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.
126 lines
3.5 KiB
Markdown
126 lines
3.5 KiB
Markdown
[← Home](../README.md) · [AmigaDOS](README.md)
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# Locks and Examine — Lock, UnLock, Examine, ExNext, ExAll
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## Overview
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AmigaDOS uses **locks** to reference files and directories. A lock is a BPTR to a `FileLock` structure. Locks provide exclusive or shared access and are used for directory scanning, attribute reading, and path resolution.
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---
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## Lock Types
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```c
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/* dos/dos.h */
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#define SHARED_LOCK -2 /* read-only; multiple readers allowed */
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#define ACCESS_READ SHARED_LOCK
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#define EXCLUSIVE_LOCK -1 /* read/write; only one holder */
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#define ACCESS_WRITE EXCLUSIVE_LOCK
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```
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---
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## Core Functions
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| LVO | Function | Registers | Returns |
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|---|---|---|---|
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| −84 | `Lock(name, mode)` | D1=name, D2=mode | D0=lock BPTR (0=fail) |
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| −90 | `UnLock(lock)` | D1=lock | — |
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| −96 | `DupLock(lock)` | D1=lock | D0=new lock |
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| −102 | `Examine(lock, fib)` | D1=lock, D2=fib | D0=BOOL |
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| −108 | `ExNext(lock, fib)` | D1=lock, D2=fib | D0=BOOL |
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| −78 | `CurrentDir(lock)` | D1=lock | D0=old lock |
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| −654 | `ExAll(lock, buf, size, type, ctrl)` | D1–D5 | D0=BOOL |
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---
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## struct FileInfoBlock
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```c
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/* dos/dos.h — NDK39 */
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struct FileInfoBlock {
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LONG fib_DiskKey; /* handler-private key */
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LONG fib_DirEntryType; /* >0 = directory, <0 = file */
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char fib_FileName[108]; /* null-terminated name */
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LONG fib_Protection; /* rwed bits */
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LONG fib_EntryType; /* same as DirEntryType */
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LONG fib_Size; /* file size in bytes */
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LONG fib_NumBlocks; /* blocks used */
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struct DateStamp fib_Date; /* modification date */
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char fib_Comment[80]; /* file comment string */
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UWORD fib_OwnerUID;
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UWORD fib_OwnerGID;
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char fib_Reserved[32];
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};
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```
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> [!IMPORTANT]
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> `FileInfoBlock` must be longword-aligned. Use `AllocDosObject(DOS_FIB, NULL)` on OS 2.0+ or `AllocMem(sizeof(struct FileInfoBlock), MEMF_PUBLIC)`.
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---
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## Protection Bits
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```c
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/* dos/dos.h */
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#define FIBF_SCRIPT (1<<6) /* s — script (executable script) */
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#define FIBF_PURE (1<<5) /* p — pure (re-entrant) */
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#define FIBF_ARCHIVE (1<<4) /* a — archived */
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#define FIBF_READ (1<<3) /* r — readable (0=allowed, 1=denied!) */
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#define FIBF_WRITE (1<<2) /* w — writable */
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#define FIBF_EXECUTE (1<<1) /* e — executable */
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#define FIBF_DELETE (1<<0) /* d — deletable */
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```
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> [!WARNING]
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> Amiga protection bits are **inverted** from Unix: bit SET means access is **denied**.
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---
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## Directory Scanning
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```c
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BPTR lock = Lock("SYS:", SHARED_LOCK);
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struct FileInfoBlock *fib = AllocDosObject(DOS_FIB, NULL);
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if (Examine(lock, fib)) { /* read dir's own info */
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while (ExNext(lock, fib)) { /* iterate entries */
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Printf("%-30s %8ld %s\n",
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fib->fib_FileName,
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fib->fib_Size,
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fib->fib_DirEntryType > 0 ? "(dir)" : "");
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}
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/* ExNext returns FALSE when done; IoErr() == ERROR_NO_MORE_ENTRIES */
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}
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FreeDosObject(DOS_FIB, fib);
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UnLock(lock);
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```
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---
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## ExAll (OS 2.0+) — Bulk Scan
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```c
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struct ExAllControl *eac = AllocDosObject(DOS_EXALLCONTROL, NULL);
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UBYTE buf[4096];
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BOOL more;
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eac->eac_LastKey = 0;
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do {
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more = ExAll(lock, buf, sizeof(buf), ED_NAME, eac);
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struct ExAllData *ead = (struct ExAllData *)buf;
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while (ead) {
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Printf("%s\n", ead->ed_Name);
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ead = ead->ed_Next;
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}
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} while (more);
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FreeDosObject(DOS_EXALLCONTROL, eac);
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```
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---
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## References
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- NDK39: `dos/dos.h`, `dos/dosextens.h`, `dos/exall.h`
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- ADCD 2.1: `Lock`, `UnLock`, `Examine`, `ExNext`, `ExAll`
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