FreeBSD/Linux Kernel Cross Reference
sys/contrib/zstd/lib/compress/zstd_cwksp.h

     /*
      * Copyright (c) Yann Collet, Facebook, Inc.
      * All rights reserved.
      *
      * This source code is licensed under both the BSD-style license (found in the
      * LICENSE file in the root directory of this source tree) and the GPLv2 (found
      * in the COPYING file in the root directory of this source tree).
      * You may select, at your option, one of the above-listed licenses.
      */
    
    #ifndef ZSTD_CWKSP_H
    #define ZSTD_CWKSP_H
    
    /*-*************************************
    *  Dependencies
    ***************************************/
    #include "../common/zstd_internal.h"
    
    #if defined (__cplusplus)
    extern "C" {
    #endif
    
    /*-*************************************
    *  Constants
    ***************************************/
    
    /* Since the workspace is effectively its own little malloc implementation /
     * arena, when we run under ASAN, we should similarly insert redzones between
     * each internal element of the workspace, so ASAN will catch overruns that
     * reach outside an object but that stay inside the workspace.
     *
     * This defines the size of that redzone.
     */
    #ifndef ZSTD_CWKSP_ASAN_REDZONE_SIZE
    #define ZSTD_CWKSP_ASAN_REDZONE_SIZE 128
    #endif
    
    
    /* Set our tables and aligneds to align by 64 bytes */
    #define ZSTD_CWKSP_ALIGNMENT_BYTES 64
    
    /*-*************************************
    *  Structures
    ***************************************/
    typedef enum {
        ZSTD_cwksp_alloc_objects,
        ZSTD_cwksp_alloc_buffers,
        ZSTD_cwksp_alloc_aligned
    } ZSTD_cwksp_alloc_phase_e;
    
    /**
     * Used to describe whether the workspace is statically allocated (and will not
     * necessarily ever be freed), or if it's dynamically allocated and we can
     * expect a well-formed caller to free this.
     */
    typedef enum {
        ZSTD_cwksp_dynamic_alloc,
        ZSTD_cwksp_static_alloc
    } ZSTD_cwksp_static_alloc_e;
    
    /**
     * Zstd fits all its internal datastructures into a single continuous buffer,
     * so that it only needs to perform a single OS allocation (or so that a buffer
     * can be provided to it and it can perform no allocations at all). This buffer
     * is called the workspace.
     *
     * Several optimizations complicate that process of allocating memory ranges
     * from this workspace for each internal datastructure:
     *
     * - These different internal datastructures have different setup requirements:
     *
     *   - The static objects need to be cleared once and can then be trivially
     *     reused for each compression.
     *
     *   - Various buffers don't need to be initialized at all--they are always
     *     written into before they're read.
     *
     *   - The matchstate tables have a unique requirement that they don't need
     *     their memory to be totally cleared, but they do need the memory to have
     *     some bound, i.e., a guarantee that all values in the memory they've been
     *     allocated is less than some maximum value (which is the starting value
     *     for the indices that they will then use for compression). When this
     *     guarantee is provided to them, they can use the memory without any setup
     *     work. When it can't, they have to clear the area.
     *
     * - These buffers also have different alignment requirements.
     *
     * - We would like to reuse the objects in the workspace for multiple
     *   compressions without having to perform any expensive reallocation or
     *   reinitialization work.
     *
     * - We would like to be able to efficiently reuse the workspace across
     *   multiple compressions **even when the compression parameters change** and
     *   we need to resize some of the objects (where possible).
     *
     * To attempt to manage this buffer, given these constraints, the ZSTD_cwksp
     * abstraction was created. It works as follows:
     *
     * Workspace Layout:
    *
    * [                        ... workspace ...                         ]
    * [objects][tables ... ->] free space [<- ... aligned][<- ... buffers]
    *
    * The various objects that live in the workspace are divided into the
    * following categories, and are allocated separately:
    *
    * - Static objects: this is optionally the enclosing ZSTD_CCtx or ZSTD_CDict,
    *   so that literally everything fits in a single buffer. Note: if present,
    *   this must be the first object in the workspace, since ZSTD_customFree{CCtx,
    *   CDict}() rely on a pointer comparison to see whether one or two frees are
    *   required.
    *
    * - Fixed size objects: these are fixed-size, fixed-count objects that are
    *   nonetheless "dynamically" allocated in the workspace so that we can
    *   control how they're initialized separately from the broader ZSTD_CCtx.
    *   Examples:
    *   - Entropy Workspace
    *   - 2 x ZSTD_compressedBlockState_t
    *   - CDict dictionary contents
    *
    * - Tables: these are any of several different datastructures (hash tables,
    *   chain tables, binary trees) that all respect a common format: they are
    *   uint32_t arrays, all of whose values are between 0 and (nextSrc - base).
    *   Their sizes depend on the cparams. These tables are 64-byte aligned.
    *
    * - Aligned: these buffers are used for various purposes that require 4 byte
    *   alignment, but don't require any initialization before they're used. These
    *   buffers are each aligned to 64 bytes.
    *
    * - Buffers: these buffers are used for various purposes that don't require
    *   any alignment or initialization before they're used. This means they can
    *   be moved around at no cost for a new compression.
    *
    * Allocating Memory:
    *
    * The various types of objects must be allocated in order, so they can be
    * correctly packed into the workspace buffer. That order is:
    *
    * 1. Objects
    * 2. Buffers
    * 3. Aligned/Tables
    *
    * Attempts to reserve objects of different types out of order will fail.
    */
   typedef struct {
       void* workspace;
       void* workspaceEnd;
   
       void* objectEnd;
       void* tableEnd;
       void* tableValidEnd;
       void* allocStart;
   
       BYTE allocFailed;
       int workspaceOversizedDuration;
       ZSTD_cwksp_alloc_phase_e phase;
       ZSTD_cwksp_static_alloc_e isStatic;
   } ZSTD_cwksp;
   
   /*-*************************************
   *  Functions
   ***************************************/
   
   MEM_STATIC size_t ZSTD_cwksp_available_space(ZSTD_cwksp* ws);
   
   MEM_STATIC void ZSTD_cwksp_assert_internal_consistency(ZSTD_cwksp* ws) {
       (void)ws;
       assert(ws->workspace <= ws->objectEnd);
       assert(ws->objectEnd <= ws->tableEnd);
       assert(ws->objectEnd <= ws->tableValidEnd);
       assert(ws->tableEnd <= ws->allocStart);
       assert(ws->tableValidEnd <= ws->allocStart);
       assert(ws->allocStart <= ws->workspaceEnd);
   }
   
   /**
    * Align must be a power of 2.
    */
   MEM_STATIC size_t ZSTD_cwksp_align(size_t size, size_t const align) {
       size_t const mask = align - 1;
       assert((align & mask) == 0);
       return (size + mask) & ~mask;
   }
   
   /**
    * Use this to determine how much space in the workspace we will consume to
    * allocate this object. (Normally it should be exactly the size of the object,
    * but under special conditions, like ASAN, where we pad each object, it might
    * be larger.)
    *
    * Since tables aren't currently redzoned, you don't need to call through this
    * to figure out how much space you need for the matchState tables. Everything
    * else is though.
    *
    * Do not use for sizing aligned buffers. Instead, use ZSTD_cwksp_aligned_alloc_size().
    */
   MEM_STATIC size_t ZSTD_cwksp_alloc_size(size_t size) {
       if (size == 0)
           return 0;
   #if ZSTD_ADDRESS_SANITIZER && !defined (ZSTD_ASAN_DONT_POISON_WORKSPACE)
       return size + 2 * ZSTD_CWKSP_ASAN_REDZONE_SIZE;
   #else
       return size;
   #endif
   }
   
   /**
    * Returns an adjusted alloc size that is the nearest larger multiple of 64 bytes.
    * Used to determine the number of bytes required for a given "aligned".
    */
   MEM_STATIC size_t ZSTD_cwksp_aligned_alloc_size(size_t size) {
       return ZSTD_cwksp_alloc_size(ZSTD_cwksp_align(size, ZSTD_CWKSP_ALIGNMENT_BYTES));
   }
   
   /**
    * Returns the amount of additional space the cwksp must allocate
    * for internal purposes (currently only alignment).
    */
   MEM_STATIC size_t ZSTD_cwksp_slack_space_required(void) {
       /* For alignment, the wksp will always allocate an additional n_1=[1, 64] bytes
        * to align the beginning of tables section, as well as another n_2=[0, 63] bytes
        * to align the beginning of the aligned section.
        *
        * n_1 + n_2 == 64 bytes if the cwksp is freshly allocated, due to tables and
        * aligneds being sized in multiples of 64 bytes.
        */
       size_t const slackSpace = ZSTD_CWKSP_ALIGNMENT_BYTES;
       return slackSpace;
   }
   
   
   /**
    * Return the number of additional bytes required to align a pointer to the given number of bytes.
    * alignBytes must be a power of two.
    */
   MEM_STATIC size_t ZSTD_cwksp_bytes_to_align_ptr(void* ptr, const size_t alignBytes) {
       size_t const alignBytesMask = alignBytes - 1;
       size_t const bytes = (alignBytes - ((size_t)ptr & (alignBytesMask))) & alignBytesMask;
       assert((alignBytes & alignBytesMask) == 0);
       assert(bytes != ZSTD_CWKSP_ALIGNMENT_BYTES);
       return bytes;
   }
   
   /**
    * Internal function. Do not use directly.
    * Reserves the given number of bytes within the aligned/buffer segment of the wksp,
    * which counts from the end of the wksp (as opposed to the object/table segment).
    *
    * Returns a pointer to the beginning of that space.
    */
   MEM_STATIC void*
   ZSTD_cwksp_reserve_internal_buffer_space(ZSTD_cwksp* ws, size_t const bytes)
   {
       void* const alloc = (BYTE*)ws->allocStart - bytes;
       void* const bottom = ws->tableEnd;
       DEBUGLOG(5, "cwksp: reserving %p %zd bytes, %zd bytes remaining",
           alloc, bytes, ZSTD_cwksp_available_space(ws) - bytes);
       ZSTD_cwksp_assert_internal_consistency(ws);
       assert(alloc >= bottom);
       if (alloc < bottom) {
           DEBUGLOG(4, "cwksp: alloc failed!");
           ws->allocFailed = 1;
           return NULL;
       }
       /* the area is reserved from the end of wksp.
        * If it overlaps with tableValidEnd, it voids guarantees on values' range */
       if (alloc < ws->tableValidEnd) {
           ws->tableValidEnd = alloc;
       }
       ws->allocStart = alloc;
       return alloc;
   }
   
   /**
    * Moves the cwksp to the next phase, and does any necessary allocations.
    * cwksp initialization must necessarily go through each phase in order.
    * Returns a 0 on success, or zstd error
    */
   MEM_STATIC size_t
   ZSTD_cwksp_internal_advance_phase(ZSTD_cwksp* ws, ZSTD_cwksp_alloc_phase_e phase)
   {
       assert(phase >= ws->phase);
       if (phase > ws->phase) {
           /* Going from allocating objects to allocating buffers */
           if (ws->phase < ZSTD_cwksp_alloc_buffers &&
                   phase >= ZSTD_cwksp_alloc_buffers) {
               ws->tableValidEnd = ws->objectEnd;
           }
   
           /* Going from allocating buffers to allocating aligneds/tables */
           if (ws->phase < ZSTD_cwksp_alloc_aligned &&
                   phase >= ZSTD_cwksp_alloc_aligned) {
               {   /* Align the start of the "aligned" to 64 bytes. Use [1, 64] bytes. */
                   size_t const bytesToAlign =
                       ZSTD_CWKSP_ALIGNMENT_BYTES - ZSTD_cwksp_bytes_to_align_ptr(ws->allocStart, ZSTD_CWKSP_ALIGNMENT_BYTES);
                   DEBUGLOG(5, "reserving aligned alignment addtl space: %zu", bytesToAlign);
                   ZSTD_STATIC_ASSERT((ZSTD_CWKSP_ALIGNMENT_BYTES & (ZSTD_CWKSP_ALIGNMENT_BYTES - 1)) == 0); /* power of 2 */
                   RETURN_ERROR_IF(!ZSTD_cwksp_reserve_internal_buffer_space(ws, bytesToAlign),
                                   memory_allocation, "aligned phase - alignment initial allocation failed!");
               }
               {   /* Align the start of the tables to 64 bytes. Use [0, 63] bytes */
                   void* const alloc = ws->objectEnd;
                   size_t const bytesToAlign = ZSTD_cwksp_bytes_to_align_ptr(alloc, ZSTD_CWKSP_ALIGNMENT_BYTES);
                   void* const objectEnd = (BYTE*)alloc + bytesToAlign;
                   DEBUGLOG(5, "reserving table alignment addtl space: %zu", bytesToAlign);
                   RETURN_ERROR_IF(objectEnd > ws->workspaceEnd, memory_allocation,
                                   "table phase - alignment initial allocation failed!");
                   ws->objectEnd = objectEnd;
                   ws->tableEnd = objectEnd;  /* table area starts being empty */
                   if (ws->tableValidEnd < ws->tableEnd) {
                       ws->tableValidEnd = ws->tableEnd;
           }   }   }
           ws->phase = phase;
           ZSTD_cwksp_assert_internal_consistency(ws);
       }
       return 0;
   }
   
   /**
    * Returns whether this object/buffer/etc was allocated in this workspace.
    */
   MEM_STATIC int ZSTD_cwksp_owns_buffer(const ZSTD_cwksp* ws, const void* ptr)
   {
       return (ptr != NULL) && (ws->workspace <= ptr) && (ptr <= ws->workspaceEnd);
   }
   
   /**
    * Internal function. Do not use directly.
    */
   MEM_STATIC void*
   ZSTD_cwksp_reserve_internal(ZSTD_cwksp* ws, size_t bytes, ZSTD_cwksp_alloc_phase_e phase)
   {
       void* alloc;
       if (ZSTD_isError(ZSTD_cwksp_internal_advance_phase(ws, phase)) || bytes == 0) {
           return NULL;
       }
   
   #if ZSTD_ADDRESS_SANITIZER && !defined (ZSTD_ASAN_DONT_POISON_WORKSPACE)
       /* over-reserve space */
       bytes += 2 * ZSTD_CWKSP_ASAN_REDZONE_SIZE;
   #endif
   
       alloc = ZSTD_cwksp_reserve_internal_buffer_space(ws, bytes);
   
   #if ZSTD_ADDRESS_SANITIZER && !defined (ZSTD_ASAN_DONT_POISON_WORKSPACE)
       /* Move alloc so there's ZSTD_CWKSP_ASAN_REDZONE_SIZE unused space on
        * either size. */
       if (alloc) {
           alloc = (BYTE *)alloc + ZSTD_CWKSP_ASAN_REDZONE_SIZE;
           if (ws->isStatic == ZSTD_cwksp_dynamic_alloc) {
               __asan_unpoison_memory_region(alloc, bytes);
           }
       }
   #endif
   
       return alloc;
   }
   
   /**
    * Reserves and returns unaligned memory.
    */
   MEM_STATIC BYTE* ZSTD_cwksp_reserve_buffer(ZSTD_cwksp* ws, size_t bytes)
   {
       return (BYTE*)ZSTD_cwksp_reserve_internal(ws, bytes, ZSTD_cwksp_alloc_buffers);
   }
   
   /**
    * Reserves and returns memory sized on and aligned on ZSTD_CWKSP_ALIGNMENT_BYTES (64 bytes).
    */
   MEM_STATIC void* ZSTD_cwksp_reserve_aligned(ZSTD_cwksp* ws, size_t bytes)
   {
       void* ptr = ZSTD_cwksp_reserve_internal(ws, ZSTD_cwksp_align(bytes, ZSTD_CWKSP_ALIGNMENT_BYTES),
                                               ZSTD_cwksp_alloc_aligned);
       assert(((size_t)ptr & (ZSTD_CWKSP_ALIGNMENT_BYTES-1))== 0);
       return ptr;
   }
   
   /**
    * Aligned on 64 bytes. These buffers have the special property that
    * their values remain constrained, allowing us to re-use them without
    * memset()-ing them.
    */
   MEM_STATIC void* ZSTD_cwksp_reserve_table(ZSTD_cwksp* ws, size_t bytes)
   {
       const ZSTD_cwksp_alloc_phase_e phase = ZSTD_cwksp_alloc_aligned;
       void* alloc;
       void* end;
       void* top;
   
       if (ZSTD_isError(ZSTD_cwksp_internal_advance_phase(ws, phase))) {
           return NULL;
       }
       alloc = ws->tableEnd;
       end = (BYTE *)alloc + bytes;
       top = ws->allocStart;
   
       DEBUGLOG(5, "cwksp: reserving %p table %zd bytes, %zd bytes remaining",
           alloc, bytes, ZSTD_cwksp_available_space(ws) - bytes);
       assert((bytes & (sizeof(U32)-1)) == 0);
       ZSTD_cwksp_assert_internal_consistency(ws);
       assert(end <= top);
       if (end > top) {
           DEBUGLOG(4, "cwksp: table alloc failed!");
           ws->allocFailed = 1;
           return NULL;
       }
       ws->tableEnd = end;
   
   #if ZSTD_ADDRESS_SANITIZER && !defined (ZSTD_ASAN_DONT_POISON_WORKSPACE)
       if (ws->isStatic == ZSTD_cwksp_dynamic_alloc) {
           __asan_unpoison_memory_region(alloc, bytes);
       }
   #endif
   
       assert((bytes & (ZSTD_CWKSP_ALIGNMENT_BYTES-1)) == 0);
       assert(((size_t)alloc & (ZSTD_CWKSP_ALIGNMENT_BYTES-1))== 0);
       return alloc;
   }
   
   /**
    * Aligned on sizeof(void*).
    * Note : should happen only once, at workspace first initialization
    */
   MEM_STATIC void* ZSTD_cwksp_reserve_object(ZSTD_cwksp* ws, size_t bytes)
   {
       size_t const roundedBytes = ZSTD_cwksp_align(bytes, sizeof(void*));
       void* alloc = ws->objectEnd;
       void* end = (BYTE*)alloc + roundedBytes;
   
   #if ZSTD_ADDRESS_SANITIZER && !defined (ZSTD_ASAN_DONT_POISON_WORKSPACE)
       /* over-reserve space */
       end = (BYTE *)end + 2 * ZSTD_CWKSP_ASAN_REDZONE_SIZE;
   #endif
   
       DEBUGLOG(4,
           "cwksp: reserving %p object %zd bytes (rounded to %zd), %zd bytes remaining",
           alloc, bytes, roundedBytes, ZSTD_cwksp_available_space(ws) - roundedBytes);
       assert((size_t)alloc % ZSTD_ALIGNOF(void*) == 0);
       assert(bytes % ZSTD_ALIGNOF(void*) == 0);
       ZSTD_cwksp_assert_internal_consistency(ws);
       /* we must be in the first phase, no advance is possible */
       if (ws->phase != ZSTD_cwksp_alloc_objects || end > ws->workspaceEnd) {
           DEBUGLOG(3, "cwksp: object alloc failed!");
           ws->allocFailed = 1;
           return NULL;
       }
       ws->objectEnd = end;
       ws->tableEnd = end;
       ws->tableValidEnd = end;
   
   #if ZSTD_ADDRESS_SANITIZER && !defined (ZSTD_ASAN_DONT_POISON_WORKSPACE)
       /* Move alloc so there's ZSTD_CWKSP_ASAN_REDZONE_SIZE unused space on
        * either size. */
       alloc = (BYTE*)alloc + ZSTD_CWKSP_ASAN_REDZONE_SIZE;
       if (ws->isStatic == ZSTD_cwksp_dynamic_alloc) {
           __asan_unpoison_memory_region(alloc, bytes);
       }
   #endif
   
       return alloc;
   }
   
   MEM_STATIC void ZSTD_cwksp_mark_tables_dirty(ZSTD_cwksp* ws)
   {
       DEBUGLOG(4, "cwksp: ZSTD_cwksp_mark_tables_dirty");
   
   #if ZSTD_MEMORY_SANITIZER && !defined (ZSTD_MSAN_DONT_POISON_WORKSPACE)
       /* To validate that the table re-use logic is sound, and that we don't
        * access table space that we haven't cleaned, we re-"poison" the table
        * space every time we mark it dirty. */
       {
           size_t size = (BYTE*)ws->tableValidEnd - (BYTE*)ws->objectEnd;
           assert(__msan_test_shadow(ws->objectEnd, size) == -1);
           __msan_poison(ws->objectEnd, size);
       }
   #endif
   
       assert(ws->tableValidEnd >= ws->objectEnd);
       assert(ws->tableValidEnd <= ws->allocStart);
       ws->tableValidEnd = ws->objectEnd;
       ZSTD_cwksp_assert_internal_consistency(ws);
   }
   
   MEM_STATIC void ZSTD_cwksp_mark_tables_clean(ZSTD_cwksp* ws) {
       DEBUGLOG(4, "cwksp: ZSTD_cwksp_mark_tables_clean");
       assert(ws->tableValidEnd >= ws->objectEnd);
       assert(ws->tableValidEnd <= ws->allocStart);
       if (ws->tableValidEnd < ws->tableEnd) {
           ws->tableValidEnd = ws->tableEnd;
       }
       ZSTD_cwksp_assert_internal_consistency(ws);
   }
   
   /**
    * Zero the part of the allocated tables not already marked clean.
    */
   MEM_STATIC void ZSTD_cwksp_clean_tables(ZSTD_cwksp* ws) {
       DEBUGLOG(4, "cwksp: ZSTD_cwksp_clean_tables");
       assert(ws->tableValidEnd >= ws->objectEnd);
       assert(ws->tableValidEnd <= ws->allocStart);
       if (ws->tableValidEnd < ws->tableEnd) {
           ZSTD_memset(ws->tableValidEnd, 0, (BYTE*)ws->tableEnd - (BYTE*)ws->tableValidEnd);
       }
       ZSTD_cwksp_mark_tables_clean(ws);
   }
   
   /**
    * Invalidates table allocations.
    * All other allocations remain valid.
    */
   MEM_STATIC void ZSTD_cwksp_clear_tables(ZSTD_cwksp* ws) {
       DEBUGLOG(4, "cwksp: clearing tables!");
   
   #if ZSTD_ADDRESS_SANITIZER && !defined (ZSTD_ASAN_DONT_POISON_WORKSPACE)
       /* We don't do this when the workspace is statically allocated, because
        * when that is the case, we have no capability to hook into the end of the
        * workspace's lifecycle to unpoison the memory.
        */
       if (ws->isStatic == ZSTD_cwksp_dynamic_alloc) {
           size_t size = (BYTE*)ws->tableValidEnd - (BYTE*)ws->objectEnd;
           __asan_poison_memory_region(ws->objectEnd, size);
       }
   #endif
   
       ws->tableEnd = ws->objectEnd;
       ZSTD_cwksp_assert_internal_consistency(ws);
   }
   
   /**
    * Invalidates all buffer, aligned, and table allocations.
    * Object allocations remain valid.
    */
   MEM_STATIC void ZSTD_cwksp_clear(ZSTD_cwksp* ws) {
       DEBUGLOG(4, "cwksp: clearing!");
   
   #if ZSTD_MEMORY_SANITIZER && !defined (ZSTD_MSAN_DONT_POISON_WORKSPACE)
       /* To validate that the context re-use logic is sound, and that we don't
        * access stuff that this compression hasn't initialized, we re-"poison"
        * the workspace (or at least the non-static, non-table parts of it)
        * every time we start a new compression. */
       {
           size_t size = (BYTE*)ws->workspaceEnd - (BYTE*)ws->tableValidEnd;
           __msan_poison(ws->tableValidEnd, size);
       }
   #endif
   
   #if ZSTD_ADDRESS_SANITIZER && !defined (ZSTD_ASAN_DONT_POISON_WORKSPACE)
       /* We don't do this when the workspace is statically allocated, because
        * when that is the case, we have no capability to hook into the end of the
        * workspace's lifecycle to unpoison the memory.
        */
       if (ws->isStatic == ZSTD_cwksp_dynamic_alloc) {
           size_t size = (BYTE*)ws->workspaceEnd - (BYTE*)ws->objectEnd;
           __asan_poison_memory_region(ws->objectEnd, size);
       }
   #endif
   
       ws->tableEnd = ws->objectEnd;
       ws->allocStart = ws->workspaceEnd;
       ws->allocFailed = 0;
       if (ws->phase > ZSTD_cwksp_alloc_buffers) {
           ws->phase = ZSTD_cwksp_alloc_buffers;
       }
       ZSTD_cwksp_assert_internal_consistency(ws);
   }
   
   /**
    * The provided workspace takes ownership of the buffer [start, start+size).
    * Any existing values in the workspace are ignored (the previously managed
    * buffer, if present, must be separately freed).
    */
   MEM_STATIC void ZSTD_cwksp_init(ZSTD_cwksp* ws, void* start, size_t size, ZSTD_cwksp_static_alloc_e isStatic) {
       DEBUGLOG(4, "cwksp: init'ing workspace with %zd bytes", size);
       assert(((size_t)start & (sizeof(void*)-1)) == 0); /* ensure correct alignment */
       ws->workspace = start;
       ws->workspaceEnd = (BYTE*)start + size;
       ws->objectEnd = ws->workspace;
       ws->tableValidEnd = ws->objectEnd;
       ws->phase = ZSTD_cwksp_alloc_objects;
       ws->isStatic = isStatic;
       ZSTD_cwksp_clear(ws);
       ws->workspaceOversizedDuration = 0;
       ZSTD_cwksp_assert_internal_consistency(ws);
   }
   
   MEM_STATIC size_t ZSTD_cwksp_create(ZSTD_cwksp* ws, size_t size, ZSTD_customMem customMem) {
       void* workspace = ZSTD_customMalloc(size, customMem);
       DEBUGLOG(4, "cwksp: creating new workspace with %zd bytes", size);
       RETURN_ERROR_IF(workspace == NULL, memory_allocation, "NULL pointer!");
       ZSTD_cwksp_init(ws, workspace, size, ZSTD_cwksp_dynamic_alloc);
       return 0;
   }
   
   MEM_STATIC void ZSTD_cwksp_free(ZSTD_cwksp* ws, ZSTD_customMem customMem) {
       void *ptr = ws->workspace;
       DEBUGLOG(4, "cwksp: freeing workspace");
       ZSTD_memset(ws, 0, sizeof(ZSTD_cwksp));
       ZSTD_customFree(ptr, customMem);
   }
   
   /**
    * Moves the management of a workspace from one cwksp to another. The src cwksp
    * is left in an invalid state (src must be re-init()'ed before it's used again).
    */
   MEM_STATIC void ZSTD_cwksp_move(ZSTD_cwksp* dst, ZSTD_cwksp* src) {
       *dst = *src;
       ZSTD_memset(src, 0, sizeof(ZSTD_cwksp));
   }
   
   MEM_STATIC size_t ZSTD_cwksp_sizeof(const ZSTD_cwksp* ws) {
       return (size_t)((BYTE*)ws->workspaceEnd - (BYTE*)ws->workspace);
   }
   
   MEM_STATIC size_t ZSTD_cwksp_used(const ZSTD_cwksp* ws) {
       return (size_t)((BYTE*)ws->tableEnd - (BYTE*)ws->workspace)
            + (size_t)((BYTE*)ws->workspaceEnd - (BYTE*)ws->allocStart);
   }
   
   MEM_STATIC int ZSTD_cwksp_reserve_failed(const ZSTD_cwksp* ws) {
       return ws->allocFailed;
   }
   
   /*-*************************************
   *  Functions Checking Free Space
   ***************************************/
   
   /* ZSTD_alignmentSpaceWithinBounds() :
    * Returns if the estimated space needed for a wksp is within an acceptable limit of the
    * actual amount of space used.
    */
   MEM_STATIC int ZSTD_cwksp_estimated_space_within_bounds(const ZSTD_cwksp* const ws,
                                                           size_t const estimatedSpace, int resizedWorkspace) {
       if (resizedWorkspace) {
           /* Resized/newly allocated wksp should have exact bounds */
           return ZSTD_cwksp_used(ws) == estimatedSpace;
       } else {
           /* Due to alignment, when reusing a workspace, we can actually consume 63 fewer or more bytes
            * than estimatedSpace. See the comments in zstd_cwksp.h for details.
            */
           return (ZSTD_cwksp_used(ws) >= estimatedSpace - 63) && (ZSTD_cwksp_used(ws) <= estimatedSpace + 63);
       }
   }
   
   
   MEM_STATIC size_t ZSTD_cwksp_available_space(ZSTD_cwksp* ws) {
       return (size_t)((BYTE*)ws->allocStart - (BYTE*)ws->tableEnd);
   }
   
   MEM_STATIC int ZSTD_cwksp_check_available(ZSTD_cwksp* ws, size_t additionalNeededSpace) {
       return ZSTD_cwksp_available_space(ws) >= additionalNeededSpace;
   }
   
   MEM_STATIC int ZSTD_cwksp_check_too_large(ZSTD_cwksp* ws, size_t additionalNeededSpace) {
       return ZSTD_cwksp_check_available(
           ws, additionalNeededSpace * ZSTD_WORKSPACETOOLARGE_FACTOR);
   }
   
   MEM_STATIC int ZSTD_cwksp_check_wasteful(ZSTD_cwksp* ws, size_t additionalNeededSpace) {
       return ZSTD_cwksp_check_too_large(ws, additionalNeededSpace)
           && ws->workspaceOversizedDuration > ZSTD_WORKSPACETOOLARGE_MAXDURATION;
   }
   
   MEM_STATIC void ZSTD_cwksp_bump_oversized_duration(
           ZSTD_cwksp* ws, size_t additionalNeededSpace) {
       if (ZSTD_cwksp_check_too_large(ws, additionalNeededSpace)) {
           ws->workspaceOversizedDuration++;
       } else {
           ws->workspaceOversizedDuration = 0;
       }
   }
   
   #if defined (__cplusplus)
   }
   #endif
   
   #endif /* ZSTD_CWKSP_H */

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