HPDFTransferStream 函数

Transfers bytes from the current source position to the current destination position and avoids an intermediate copy for supported storage types

声明

function HPDFTransferStream(
  Source, Destination: TStream;
  Count: Int64 = -1): Int64;

单元

HPDFObjs

Transfer paths

• TMemoryStream writes directly from its backing pointer without allocating a transfer buffer
• TFileStream writes directly from bounded read-only mapped views and falls back automatically when mapping is unavailable
• THPDFMappedFileStream and source-backed THPDFLazyFileStream write directly from resident mapped windows
• Random-access streams delegate to THPDFRandomAccessSource.TransferAt，而 THPDFCoalescingRandomAccessSource writes retained cache blocks directly
• Other stream classes use a bounded 64 KiB fallback buffer

Count and positions

A Count of -1 transfers all bytes remaining from the current source position, zero transfers nothing, and a positive value is capped at the available bytes; values below -1 are rejected

Both stream positions advance by the number of bytes returned; source and destination must be different non-nil objects

PDF writer integration

Unencrypted PDF stream bodies, filter-free decoded output, raw loaded-image export, lazy-stream materialisation, and adaptive temporary-stream spill use this transfer layer automatically

Encrypted stream bodies still require transformation staging because their bytes and length change before serialization

相关 API

• THPDFRandomAccessSource 类
• THPDFCoalescingRandomAccessSource Class
• THotPDF.OpenLoadedStreamSourceSlice Method
• 窗口化本地文件映射
• 目录