90 lines
2.8 KiB
C
90 lines
2.8 KiB
C
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/**
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* @file ptr_conversion_box.h
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* @brief Box 3: Unified Pointer Conversion Layer
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*
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* MISSION: Fix BASE/USER pointer confusion across codebase
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*
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* DESIGN:
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* - BASE pointer: Points to start of block in storage (0-byte aligned)
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* - USER pointer: Points to usable memory (+1 byte for classes 0-6, +0 for class 7)
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* - Class 7 (2KB) is headerless (no +1 offset)
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* - Classes 0-6 have 1-byte header (need +1 offset)
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*
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* BOX BOUNDARIES:
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* - Box 1 (Front Gate) → Box 3 → Box 4 (User) [BASE to USER]
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* - Box 4 (User) → Box 3 → Box 1 (Front Gate) [USER to BASE]
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*/
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#ifndef HAKMEM_PTR_CONVERSION_BOX_H
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#define HAKMEM_PTR_CONVERSION_BOX_H
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#include <stdint.h>
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#include <stddef.h>
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#ifdef HAKMEM_PTR_CONVERSION_DEBUG
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#include <stdio.h>
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#define PTR_CONV_LOG(...) fprintf(stderr, "[PTR_CONV] " __VA_ARGS__)
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#else
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#define PTR_CONV_LOG(...) ((void)0)
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#endif
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/**
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* Convert BASE pointer (storage) to USER pointer (returned to caller)
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*
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* @param base_ptr Pointer to block in storage (no offset)
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* @param class_idx Size class (0-6: +1 offset, 7: +0 offset)
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* @return USER pointer (usable memory address)
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*/
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static inline void* ptr_base_to_user(void* base_ptr, uint8_t class_idx) {
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if (base_ptr == NULL) {
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return NULL;
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}
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/* Class 7 (2KB) is headerless - no offset */
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if (class_idx == 7) {
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PTR_CONV_LOG("BASE→USER cls=%u base=%p → user=%p (headerless)\n",
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class_idx, base_ptr, base_ptr);
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return base_ptr;
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}
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/* Classes 0-6 have 1-byte header - skip it */
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void* user_ptr = (void*)((uint8_t*)base_ptr + 1);
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PTR_CONV_LOG("BASE→USER cls=%u base=%p → user=%p (+1 offset)\n",
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class_idx, base_ptr, user_ptr);
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return user_ptr;
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}
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/**
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* Convert USER pointer (from caller) to BASE pointer (storage)
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*
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* @param user_ptr Pointer from user (may have +1 offset)
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* @param class_idx Size class (0-6: -1 offset, 7: -0 offset)
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* @return BASE pointer (block start in storage)
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*/
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static inline void* ptr_user_to_base(void* user_ptr, uint8_t class_idx) {
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if (user_ptr == NULL) {
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return NULL;
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}
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/* Class 7 (2KB) is headerless - no offset */
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if (class_idx == 7) {
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PTR_CONV_LOG("USER→BASE cls=%u user=%p → base=%p (headerless)\n",
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class_idx, user_ptr, user_ptr);
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return user_ptr;
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}
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/* Classes 0-6 have 1-byte header - rewind it */
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void* base_ptr = (void*)((uint8_t*)user_ptr - 1);
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PTR_CONV_LOG("USER→BASE cls=%u user=%p → base=%p (-1 offset)\n",
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class_idx, user_ptr, base_ptr);
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return base_ptr;
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}
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/**
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* Convenience macros for cleaner call sites
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*/
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#define PTR_BASE_TO_USER(base, cls) ptr_base_to_user((base), (cls))
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#define PTR_USER_TO_BASE(user, cls) ptr_user_to_base((user), (cls))
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#endif /* HAKMEM_PTR_CONVERSION_BOX_H */
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