From 57abba86083cd65d73e0df3bc12bd9560c178f21 Mon Sep 17 00:00:00 2001
From: midipix <writeonce@midipix.org>
Date: Jul 18 2024 06:50:45 +0000
Subject: driver: allocate source data cache buffer as needed.


---

diff --git a/src/driver/tpax_driver_ctx.c b/src/driver/tpax_driver_ctx.c
index aaaea59..4348ebc 100644
--- a/src/driver/tpax_driver_ctx.c
+++ b/src/driver/tpax_driver_ctx.c
@@ -34,6 +34,9 @@
 	| TPAX_DRIVER_WRITE_FORMAT_USTAR \
 	| TPAX_DRIVER_WRITE_FORMAT_RUSTAR)
 
+#define TPAX_CACHE_MIN (1 << 12)
+#define TPAX_CACHE_MAX (1 << 24)
+
 /* package info */
 static const struct tpax_source_version tpax_src_version = {
 	TPAX_TAG_VER_MAJOR,
@@ -608,6 +611,30 @@ static int tpax_driver_srcstat_error(
 	return TPAX_ERROR;
 }
 
+static int tpax_driver_cache_error(
+	struct tpax_driver_ctx_impl *   ctx,
+	const char *                    program)
+{
+	int             lerrno;
+	const char *    errstr;
+
+	lerrno = errno;
+	errno  = 0;
+
+	errstr = strerror(lerrno);
+	errstr = errno ? tpax_null_errdesc : errstr;
+	errno  = lerrno;
+
+	tpax_dprintf(
+		ctx->fdctx.fderr,
+		"%s: failed to allocate source data cache (%s).\n",
+		program,errstr);
+
+	tpax_lib_free_driver_ctx(&ctx->ctx);
+
+	return TPAX_ERROR;
+}
+
 int tpax_lib_get_driver_ctx(
 	char **				argv,
 	char **				envp,
@@ -627,6 +654,7 @@ int tpax_lib_get_driver_ctx(
 	size_t				nunits;
 	size_t                          nreplstr;
 	size_t                          sreplstr;
+	size_t                          cachesize;
 	const char *			program;
 	int				fddst;
 	const char *			ch;
@@ -957,6 +985,21 @@ int tpax_lib_get_driver_ctx(
 		}
 	}
 
+	/* allocate source data cache as needed */
+	if (ctx->cctx.srcflags == TPAX_SOURCE_DATA_FILEIO) {
+		cachesize = TPAX_CACHE_MAX;
+
+		for (; !ctx->cacheaddr && (cachesize >= TPAX_CACHE_MIN); )
+			if (!(ctx->cacheaddr = calloc(cachesize,1)))
+				cachesize >>= 1;
+
+		if (!ctx->cacheaddr)
+			return tpax_driver_cache_error(ctx,program);
+
+		ctx->cachemark = ctx->cacheaddr;
+		ctx->cachecap  = &ctx->cacheaddr[cachesize];
+	}
+
 	/* all done */
 	if (archive) {
 		ctx->file     = archive->arg;
@@ -998,6 +1041,9 @@ static void tpax_free_driver_ctx_impl(struct tpax_driver_ctx_alloc * ictx)
 	if (ictx->ctx.keyvalv)
 		free(ictx->ctx.keyvalv);
 
+	if (ictx->ctx.cacheaddr)
+		free(ictx->ctx.cacheaddr);
+
 	if (ictx->ctx.mapaddr)
 		munmap(ictx->ctx.mapaddr,ictx->ctx.mapsize);
 
diff --git a/src/internal/tpax_driver_impl.h b/src/internal/tpax_driver_impl.h
index bc3ffc2..02e0d84 100644
--- a/src/internal/tpax_driver_impl.h
+++ b/src/internal/tpax_driver_impl.h
@@ -120,6 +120,9 @@ struct tpax_driver_ctx_impl {
 	size_t                        bufsize;
 	void *                        mapaddr;
 	size_t                        mapsize;
+	char *                        cacheaddr;
+	char *                        cachemark;
+	char *                        cachecap;
 	size_t                        nqueued;
 	off_t                         cpos;
 };