/* zutil.h -- internal interface and configuration of the compression library * Copyright (C) 1995-2010 Jean-loup Gailly. * For conditions of distribution and use, see copyright notice in zlib.h */ /* WARNING: this file should *not* be used by applications. It is part of the implementation of the compression library and is subject to change. Applications should only use zlib.h. */ /* @(#) $Id$ */ #ifndef ZUTIL_H #define ZUTIL_H #if ((__GNUC__-0) * 10 + __GNUC_MINOR__-0 >= 33) && !defined(NO_VIZ) # define ZLIB_INTERNAL __attribute__((visibility ("hidden"))) #else # define ZLIB_INTERNAL #endif #include "zlib.h" #ifdef STDC # if !(defined(_WIN32_WCE) && defined(_MSC_VER)) # include # endif # include # include #endif ABC_NAMESPACE_HEADER_START #ifndef local # define local static #endif /* compile with -Dlocal if your debugger can't find static symbols */ typedef unsigned char uch; typedef uch FAR uchf; typedef unsigned short ush; typedef ush FAR ushf; typedef unsigned long ulg; extern const char * const z_errmsg[10]; /* indexed by 2-zlib_error */ /* (size given to avoid silly warnings with Visual C++) */ #define ERR_MSG(err) z_errmsg[Z_NEED_DICT-(err)] #define ERR_RETURN(strm,err) \ return (strm->msg = (char*)ERR_MSG(err), (err)) /* To be used only when the state is known to be valid */ /* common constants */ #ifndef DEF_WBITS # define DEF_WBITS MAX_WBITS #endif /* default windowBits for decompression. MAX_WBITS is for compression only */ #if MAX_MEM_LEVEL >= 8 # define DEF_MEM_LEVEL 8 #else # define DEF_MEM_LEVEL MAX_MEM_LEVEL #endif /* default memLevel */ #define STORED_BLOCK 0 #define STATIC_TREES 1 #define DYN_TREES 2 /* The three kinds of block type */ #define MIN_MATCH 3 #define MAX_MATCH 258 /* The minimum and maximum match lengths */ #define PRESET_DICT 0x20 /* preset dictionary flag in zlib header */ /* target dependencies */ #if defined(MSDOS) || (defined(WINDOWS) && !defined(WIN32)) # define OS_CODE 0x00 # if defined(__TURBOC__) || defined(__BORLANDC__) # if (__STDC__ == 1) && (defined(__LARGE__) || defined(__COMPACT__)) /* Allow compilation with ANSI keywords only enabled */ void _Cdecl farfree( void *block ); void *_Cdecl farmalloc( unsigned long nbytes ); # else ABC_NAMESPACE_HEADER_END # include ABC_NAMESPACE_HEADER_START # endif # else /* MSC or DJGPP */ ABC_NAMESPACE_HEADER_END # include ABC_NAMESPACE_HEADER_START # endif #endif #ifdef AMIGA # define OS_CODE 0x01 #endif #if defined(VAXC) || defined(VMS) # define OS_CODE 0x02 # define F_OPEN(name, mode) \ fopen((name), (mode), "mbc=60", "ctx=stm", "rfm=fix", "mrs=512") #endif #if defined(ATARI) || defined(atarist) # define OS_CODE 0x05 #endif #ifdef OS2 # define OS_CODE 0x06 # ifdef M_I86 ABC_NAMESPACE_HEADER_END # include ABC_NAMESPACE_HEADER_START # endif #endif #if defined(MACOS) || defined(TARGET_OS_MAC) # define OS_CODE 0x07 # if defined(__MWERKS__) && __dest_os != __be_os && __dest_os != __win32_os ABC_NAMESPACE_HEADER_END # include /* for fdopen */ ABC_NAMESPACE_HEADER_START # else # ifndef fdopen # define fdopen(fd,mode) NULL /* No fdopen() */ # endif # endif #endif #ifdef TOPS20 # define OS_CODE 0x0a #endif #ifdef WIN32 # ifndef __CYGWIN__ /* Cygwin is Unix, not Win32 */ # define OS_CODE 0x0b # endif #endif #ifdef __50SERIES /* Prime/PRIMOS */ # define OS_CODE 0x0f #endif #if defined(_BEOS_) || defined(RISCOS) # define fdopen(fd,mode) NULL /* No fdopen() */ #endif #if (defined(_MSC_VER) && (_MSC_VER > 600)) && !defined __INTERIX # if defined(_WIN32_WCE) # define fdopen(fd,mode) NULL /* No fdopen() */ # ifndef _PTRDIFF_T_DEFINED typedef int ptrdiff_t; # define _PTRDIFF_T_DEFINED # endif # else # define fdopen(fd,type) _fdopen(fd,type) # endif #endif #if defined(__BORLANDC__) #pragma warn -8004 #pragma warn -8008 #pragma warn -8066 #endif /* provide prototypes for these when building zlib without LFS */ #if !defined(_LARGEFILE64_SOURCE) || _LFS64_LARGEFILE-0 == 0 ZEXTERN uLong ZEXPORT adler32_combine64 OF((uLong, uLong, z_off_t)); ZEXTERN uLong ZEXPORT crc32_combine64 OF((uLong, uLong, z_off_t)); #endif /* common defaults */ #ifndef OS_CODE # define OS_CODE 0x03 /* assume Unix */ #endif #ifndef F_OPEN # define F_OPEN(name, mode) fopen((name), (mode)) #endif /* functions */ #if defined(STDC99) || (defined(__TURBOC__) && __TURBOC__ >= 0x550) # ifndef HAVE_VSNPRINTF # define HAVE_VSNPRINTF # endif #endif #if defined(__CYGWIN__) # ifndef HAVE_VSNPRINTF # define HAVE_VSNPRINTF # endif #endif #ifndef HAVE_VSNPRINTF # ifdef MSDOS /* vsnprintf may exist on some MS-DOS compilers (DJGPP?), but for now we just assume it doesn't. */ # define NO_vsnprintf # endif # ifdef __TURBOC__ # define NO_vsnprintf # endif # ifdef WIN32 /* In Win32, vsnprintf is available as the "non-ANSI" _vsnprintf. */ # if !defined(vsnprintf) && !defined(NO_vsnprintf) # if !defined(_MSC_VER) || ( defined(_MSC_VER) && _MSC_VER < 1500 ) # define vsnprintf _vsnprintf # endif # endif # endif # ifdef __SASC # define NO_vsnprintf # endif #endif #ifdef VMS # define NO_vsnprintf #endif #if defined(pyr) # define NO_MEMCPY #endif #if defined(SMALL_MEDIUM) && !defined(_MSC_VER) && !defined(__SC__) /* Use our own functions for small and medium model with MSC <= 5.0. * You may have to use the same strategy for Borland C (untested). * The __SC__ check is for Symantec. */ # define NO_MEMCPY #endif #if defined(STDC) && !defined(HAVE_MEMCPY) && !defined(NO_MEMCPY) # define HAVE_MEMCPY #endif #ifdef HAVE_MEMCPY # ifdef SMALL_MEDIUM /* MSDOS small or medium model */ # define zmemcpy _fmemcpy # define zmemcmp _fmemcmp # define zmemzero(dest, len) _fmemset(dest, 0, (size_t)len) # else # define zmemcpy memcpy # define zmemcmp memcmp # define zmemzero(dest, len) memset(dest,
/**
 * Calculate virtual scroll stuffs
 *
 * @param {?Object} opts Options for calculation
 *
 * @returns {Object} result
 *
 * __opts__ should have following properties:
 * - {number}         itemCount
 * - {number}         rowHeight
 * - {number}         viewportTop
 * - {number}         viewportHeight
 * - {Array<?number>} [itemHeights]
 *
 * __result__ have following properties:
 * - {number} start
 * - {number} end
 * - {number} paddingTop
 * - {number} paddingBottom
 */
export function calcVScroll(opts) {
    if (!opts) {
        return { start: 0, end: 0, paddingTop: 0, paddingBottom: 0 };
    }

    const { itemCount, rowHeight, viewportTop, viewportHeight, itemHeights } = opts;
    const viewportBottom = viewportTop + viewportHeight;

    let start = 0;
    let end = 0;

    let paddingTop = 0;
    let paddingBottom = 0;

    if (itemHeights) {

        for (let i = 0, pos = 0; i < itemCount; i++) {
            const height = itemHeights[i] || rowHeight;

            if (pos <= viewportTop && i % 2 === 0) {
                paddingTop = pos;
                start = i;
            }

            if (pos <= viewportBottom) {
                end = i + 1;
            } else {
                paddingBottom += height;
            }

            pos += height;
        }

    } else {

        // Make sure that we start at an even row so that CSS `:nth-child(even)` is preserved
        start = Math.max(0, Math.floor(viewportTop / rowHeight) - 1) & ~1;
        end = Math.min(
            itemCount,
            start + Math.ceil(viewportHeight / rowHeight) + 2
        );

        // When a large trunk of elements is removed from the button, start may be far off the viewport.
        // To make this issue less severe, limit the top placeholder to the total number of rows.
        paddingTop = Math.min(start, itemCount) * rowHeight;
        paddingBottom = Math.max(0, itemCount - end) * rowHeight;
    }

    return { start, end, paddingTop, paddingBottom };
}
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