modify ptr_to_globals trick so that we do not violate
type safety (well, sort of ;))
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dd2b2f75ae
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@ -235,7 +235,7 @@ enum {
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};
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struct global1 {
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struct globals {
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lng block_start;
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@ -343,7 +343,6 @@ struct global1 {
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uint32_t crc; /* shift register contents */
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};
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extern struct global1 *ptr_to_globals;
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#define G1 (*(ptr_to_globals - 1))
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@ -869,7 +868,7 @@ typedef struct tree_desc {
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int max_code; /* largest code with non zero frequency */
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} tree_desc;
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struct global2 {
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struct globals2 {
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ush heap[HEAP_SIZE]; /* heap used to build the Huffman trees */
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int heap_len; /* number of elements in the heap */
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@ -956,7 +955,7 @@ struct global2 {
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ulg compressed_len; /* total bit length of compressed file */
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};
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#define G2ptr ((struct global2*)(ptr_to_globals))
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#define G2ptr ((struct globals2*)(ptr_to_globals))
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#define G2 (*G2ptr)
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@ -2048,7 +2047,7 @@ int gzip_main(int argc, char **argv)
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}
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#endif
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ptr_to_globals = xzalloc(sizeof(struct global1) + sizeof(struct global2));
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ptr_to_globals = xzalloc(sizeof(struct globals) + sizeof(struct globals2));
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ptr_to_globals++;
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G2.l_desc.dyn_tree = G2.dyn_ltree;
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G2.l_desc.static_tree = G2.static_ltree;
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@ -59,30 +59,33 @@ archival/libunarchive/decompress_unzip.c:
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This example completely eliminates globals in that module.
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Required memory is allocated in inflate_gunzip() [its main module]
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and then passed down to all subroutines which need to access globals
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and then passed down to all subroutines which need to access 'globals'
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as a parameter.
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Example 2
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In case you don't want to pass this additional parameter everywhere,
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take a look at archival/gzip.c. Here all global data is replaced by
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singe global pointer (ptr_to_globals) to allocated storage.
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single global pointer (ptr_to_globals) to allocated storage.
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In order to not duplicate ptr_to_globals in every applet, you can
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reuse single common one. It is defined in libbb/messages.c
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as void *ptr_to_globals, but is NOT declared in libbb.h.
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You first define a struct:
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as struct globals *ptr_to_globals, but the struct globals is
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NOT defined in libbb.h. You first define your own struct:
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struct my_globals { int a; char buf[1000]; };
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struct globals { int a; char buf[1000]; };
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and then declare that ptr_to_globals is a pointer to it:
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extern struct my_globals *ptr_to_globals;
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#define G (*ptr_to_globals)
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Linker magic enures that these two merge into single pointer object.
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Linker magic ensures that these two merge into single pointer object.
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Now initialize it in <applet>_main():
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ptr_to_globals = xzalloc(sizeof(G));
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and you can reference "globals" by G.a, G.buf and so on, in any function.
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The drawback is that now you have to initialize it by hand. xzalloc()
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can be helpful in clearing allocated storage to 0, but anything more
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must be done by hand.
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@ -806,6 +806,10 @@ extern const int const_int_1;
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#define BUFSIZ 4096
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#endif
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extern char bb_common_bufsiz1[BUFSIZ+1];
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/* This struct is deliberately not defined. */
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/* See docs/keep_data_small.txt */
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struct globals;
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extern struct globals *ptr_to_globals;
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/* You can change LIBBB_DEFAULT_LOGIN_SHELL, but don't use it,
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* use bb_default_login_shell and following defines.
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@ -56,4 +56,5 @@ WTMP_FILE;
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char bb_common_bufsiz1[BUFSIZ+1];
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void *ptr_to_globals;
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struct globals;
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struct globals *ptr_to_globals;
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