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--- etc:20-lpm-gui [2022/05/14 04:59] – wikiadmin
+++ etc:20-lpm-gui [2022/07/28 18:13] (current) – wikiadmin
@@ Line 55: / Line 55: @@
 As archive format, lpk uses gzip compressed cpio, prepended by a header containing the package information. The prepended header looks like this:
-  * 11 bytes made from 5 bytes containing the version signature (EPLM20) and 6 bytes containing the zero-padded size of the following header
+  * 11 bytes made from 5 bytes containing the version signature (ELPM20) and 6 bytes containing the zero-padded size of the following header
   * The package description, starting at byte 12.
@@ Line 191: / Line 191: @@
 The function plpm_exec in lpmsh.c provides a working example on how to call plpm in all cases.
-===== 8. Important data structures =====
+===== 8. Important frontend data structures =====
 ==== 8.1 LPI ====
@@ Line 278: / Line 278: @@
 - ekva_new: to create a new EKVA array \\ - ekva_addval: to add a key/val pair to the EKVA arrray \\ - ekva_getval: to read the first value for a key \\ - ekva_cntval: to count the number of vaules for a key \\ - ekva_getone: to read the specified value for a key \\ - ekva_getvals: to read all values for a key
+==== 8.3 LPA ====
+LPA arrays are used to store information about available updates in an easily parsable form:
+<code>
+struct s_lpa {
+    char action;
+    char status;
+    LPI *lpi;
+    char *candidate;
+};
+typedef struct s_lpa LPA;
+</code>
+- action is 'U' or 'I', as an update might pull a new dependency \\ - status is always 'N' \\ - lpi contains the package info of the package to be installed or updated
+===== 9. important frontend functions =====
+All frontend functions are defined int lpm.h, the ones relevant to a frontend using plpm for privileged actions are:
+- lpm_open: "opens" the local lpm repository and return an LPM * structure for further use.
+- lpmui_init: initializes the internally used lpmui, necessary, but has no effect…
+- lpm_lpc_load: loads the configured package catalogue
+- lpm_lpc_connect: connects the program to the package catalogie
+- lpm_lpc_cache_fill: fills the package catalogue cache
+- lpm_lpc_release: disconnects from the package catalogue
+- lpm_cache_free: frees the cache
+- lpk_info_ekva: converts an LPI * package description to a string-based EKVA * keyword/value list
+- lpm_list_lpi: returns a list of locally installed package descriptions
+- lpm_lpf_info: returns a package description from a package file
+- lpm_findpkg_new: returns a list of available, not installed packages
+- lconf_read: reads the lpm config file
+- log_init: initializes the internal logging mechanism, necessary
+- lpm_pre_update: checks for an available update of a specified package
+- lpm_lpa_list_add_lpt: adds the results of lpm_pre_update to an easily readable LPA * list
+===== 10. Required globals =====
+In order for the frontend to be able to use all further funtions correctly, it has to define a set of global variables:
+<code>
+void *lpc_backend_handle;
+EKVA **lpm_sys_conf = NULL;
+LPC *lpc;
+int dry_run =  0;
+int vote_mode = LPM_VOTE_DEFAULT;
+LPMUI *lpmui = NULL;
+struct s_llog *llog;
+LPI **lpc_cache;
+</code>
+===== 11. Required initialization sequence =====
+Maybe in later releases, the initialisation sequence will be simplyfied and merged into some lpm_init function, but for the moment, the code from line 490 - 542 from lpmsh.c can be copied for that purpose.