1 files changed, 144 insertions, 0 deletions
diff --git a/tools/src/minilzlib/inputbuf.c b/tools/src/minilzlib/inputbuf.c
new file mode 100644
index 0000000..67d652c
--- /dev/null
+++ b/tools/src/minilzlib/inputbuf.c
@@ -0,0 +1,144 @@
+/*++
+
+Copyright (c) Alex Ionescu.  All rights reserved.
+
+Module Name:
+
+    inputbuf.c
+
+Abstract:
+
+    This module implements helper functions for managing the input buffer that
+    contains arithmetic-coded LZ77 match distance-length pairs and raw literals
+    Both seeking (such that an external reader can refer to multiple bytes) and
+    reading (capturing) an individual byte are supported. Support for aligning
+    input data to 4 bytes (which is a requirement for XZ-encoded files) is also
+    implemented.
+
+Author:
+
+    Alex Ionescu (@aionescu) 15-Apr-2020 - Initial version
+
+Environment:
+
+    Windows & Linux, user mode and kernel mode.
+
+--*/
+
+#include "minlzlib.h"
+
+//
+// Input Buffer State
+//
+typedef struct _BUFFER_STATE
+{
+    //
+    // Start of the buffer, current offset, current packet end, and total input size
+    //
+    uint8_t* Buffer;
+    uint32_t Offset;
+    uint32_t SoftLimit;
+    uint32_t Size;
+} BUFFER_STATE, * PBUFFER_STATE;
+BUFFER_STATE In;
+
+bool
+BfAlign (
+    void
+    )
+{
+    uint8_t padByte;
+    //
+    // Keep reading until we reach 32-bit alignment. All bytes must be zero.
+    //
+    while (In.Offset & 3)
+    {
+        if (!BfRead(&padByte) || (padByte != 0))
+        {
+            return false;
+        }
+    }
+    return true;
+}
+
+bool
+BfSetSoftLimit (
+    uint32_t Remaining
+    )
+{
+    if ((In.Size - In.Offset) < Remaining)
+    {
+        return false;
+    }
+    In.SoftLimit = In.Offset + Remaining;
+    return true;
+}
+
+void
+BfResetSoftLimit (
+    void
+    )
+{
+    In.SoftLimit = In.Size;
+}
+
+bool
+BfSeek (
+    uint32_t Length,
+    uint8_t** Bytes
+    )
+{
+    //
+    // Make sure the input buffer has enough space to seek the desired size, if
+    // it does, return the current position and then seek past the desired size
+    //
+    if ((In.Offset + Length) > In.SoftLimit)
+    {
+        *Bytes = 0;
+        return false;
+    }
+    *Bytes = &In.Buffer[In.Offset];
+    In.Offset += Length;
+    return true;
+}
+
+uint32_t
+BfTell (
+    void
+    )
+{
+    return In.Offset;
+}
+
+bool
+BfRead (
+    uint8_t* Byte
+    )
+{
+    uint8_t* pByte;
+    //
+    // Seek past the byte and read it
+    //
+    if (!BfSeek(sizeof(*Byte), &pByte))
+    {
+        *Byte = 0;
+        return false;
+    }
+    *Byte = *pByte;
+    return true;
+}
+
+void
+BfInitialize (
+    uint8_t* InputBuffer,
+    uint32_t InputSize
+    )
+{
+    //
+    // Save all the data in the context buffer state
+    //
+    In.Buffer = InputBuffer;
+    In.Size = InputSize;
+    In.SoftLimit = InputSize;
+    In.Offset = 0;
+}